Bashar Abdo had just returned home last month after four years in the Syrian military when a mob of neighbors and others armed with guns and knives swarmed his family’s front door and accused him of being a thug for the ousted regime.

His sisters and sister-in-law tried to block the crowd as he hid. But people stormed in and found Mr. Abdo, 22, in the kitchen. They stabbed him before dragging him outside, even as his sister, Marwa, clung to him. There, he was shot.

The account, shared by Mr. Abdo’s family, was confirmed by local police in the northwestern city of Idlib. Video footage widely shared on Syrian social media and verified by The New York Times captured the gruesome scene that followed: As Ms. Abdo gripped his lifeless body, neighbors continued to kick him. She begged them to stop, saying he was already dead.

“This is your fate,” one man yelled. Other verified video footage shows a crowd shouting expletives after Mr. Abdo’s body was tied by the neck to a car and dragged through the streets. It is not clear who filmed the video.

Ms. Abdo recalled those moments in an interview with The Times four days later. She vowed revenge, a sign of the growing threat of a cycle of violent retribution in a new Syria.

The country is emerging suddenly and unexpectedly from 13 years of civil war and more than five decades under the Assad dynasty, which maintained its grip on power with fear, torture and mass killings.

The killing of Mr. Abdo underscores the complicated reckoning ahead in Syria, where the wounds remain fresh and anger is close to the surface. Many Syrians want accountability for crimes conducted during the civil war. Others are seeking vengeance.

At least half a million Syrians were killed during the war, most of them in airstrikes carried out by Syrian warplanes and helicopters or in prison under torture or in mass executions, according to Syrian human rights groups. Many people remain unaccounted for.

Officials with the new interim Syrian government, headed by the Islamist rebel group Hayat Tahrir al-Sham, are racing to set up courts and police forces to address decades of grievances. They are urging citizens to forgive and not take matters into their own hands.

Ahmed al-Shara, the head of the rebel alliance that overthrew the Assad government, has said that it will hunt down and prosecute senior figures for crimes that include murdering, wrongly imprisoning, torturing and gassing their own people, but that rank-and-file conscripted soldiers would receive amnesty.

In a recent interview, Mr. al-Shara said that “justice must be sought through the judiciary and the law. Not through individuals.”

“If matters are left that everyone takes revenge, we will have transformed into the law of the jungle,” he said.

Some Syrians have said that while Mr. al-Shara may choose to forgive, they will not. Last week, the mayor of Dumar, a suburb of Damascus, was killed by residents who accused him of informing on people and getting them arrested under the former government, according to the British-based Syrian Observatory for Human Rights.

Mr. Abdo was a soldier — a conscript — in the Syrian military for four years. But his family said he tried to defect twice by failing to return after he was given a few days’ leave. In the end, he spent a month in a military prison for his attempts to desert and was released when the rebels who overthrew the Assad government captured the prison as part of their lightning-fast sweep through the country, several family members said.

At first he was afraid to come home, but when he heard that Mr. al-Shara had said that soldiers like himself would be given amnesty, he felt safe enough, his family said. Not long after he got back, the mob was at the front door.

They accused him of informing on his neighbors, resulting in their being killed or imprisoned. The family said they see many of the killers every day, but they have not confronted them and are seeking to move to another neighborhood.

In response to questions about the killing, the police in Idlib, who are affiliated with Hayat Tahrir al-Sham, which has ruled the province for years, said in a statement that they were investigating the killing but that the Abdo family was “notorious for working with the regime.”

But the police said that “no one has the right to assault anyone.” No one has been arrested so far.

The family members denied that they had any connections to the regime. They also said that if their brother had worked as an enforcer, he would not have returned home. He was only a foot soldier, they said.

“We vowed that if the government doesn’t get justice, we will get our own justice,” Ms. Abdo, 32, shrieked, tears streaking her face. She slammed her fist into the carpet that she and her sisters had spent days washing to remove her brother’s blood. There was still blood in the kitchen and on some of the walls.

“We won’t let his blood be spilled with no response,” she said.

Others are using whatever means they can to try to avoid a cycle of retribution.

Muhammad al-Asmar, a media official with the new government, said he sent out a Google document to residents of his native village, Qabhani, in Hama province, to submit any grievances against fellow villagers. Mr. al-Asmar said he took the initiative after hearing that several people whom the government had relied on to abuse and intimidate Syrians had returned home after Mr. al-Assad’s fall.

“There wasn’t any response,” he said, because “people are saying, ‘I’m going to take justice into my own hands.’”

Still, he hopes that such an approach could be adopted on a national level to stem vigilante justice.

Officials with the new justice ministry admit that they were not prepared to take over governance for much of the country when they launched their offensive on Nov. 27. Efforts to maintain calm appear for now to be coming in the form of public statements or suggested sermons for imams appealing to peoples’ restraint.

“Honestly, we are under a great weight and there will be transgressions,” said Ahmad Hilal, the new head judge at the Aleppo courthouse. People who are angry over crimes during the Assad era “don’t want to wait for the courts to act — they want to take law and justice into their own hands.”

The struggle against mob justice is daunting because in every city and town, Syrians who may be accused of such crimes are returning home.

When Assad’s government fell last month, Alaa Khateeb went back to his village, Taftanaz, in the countryside of Idlib province. His family quickly started telling people that he had dodged the military for years and then deserted twice to signal that he was not a willing participant in Mr. al-Assad’s army.

“I know I haven’t done anything,” Mr. Khateeb, 25, a married father of three, said on a recent day on the outskirts of the village, working to renovate a relative’s home that Syrian soldiers had taken over and stripped.

Despite Mr. Khateeb’s protestations, he faces a cloud of suspicion. Even lowly conscripts are being blamed for enabling crimes — whether or not that is true.

One of Mr. Khateeb’s relatives, Salah Khateeb, 67, who has a produce market in the village, wasn’t sure he would even say “hi” once he heard that his second cousin had returned to Taftanaz.

“He is my relative and I was questioning if I should accept him or not,” he said. “Others might even consider taking retaliation.”

Muhammad Haj Kadour, Jacob Roubai and Nader Ibrahim contributed reporting.

It was late at night and Anton Telegin was driving toward a sprawling coal mine near Ukraine’s eastern front line, using darkness to evade Russian attack drones.

Mr. Telegin had come to collect wages for himself and some fellow miners, as he did at the end of every month. But this trip, on the day after Christmas, felt different: Russian troops were at one of the far gates of the mine, and he wondered whether it would be his last trip to the place where he had worked for 18 years. The last few months, he and his colleagues had toiled under escalating Russian attacks.

Two days earlier, a strike knocked out the plant’s electricity substation, halting operations. Sensing the end, some miners left, taking their towels and shampoo from the changing rooms where they scraped soot from themselves at the end of long shifts.

“People were packing up, already saying goodbye,” Mr. Telegin, 40, recalled.

Mr. Telegin has not returned to the mine since Christmas and is now in Kyiv. The approaching fighting kept the facility out of action and on Tuesday, Metinvest, the company that owns the mine, announced that the facility was now shut.

The closing of the mine, located just southeast of the embattled city of Pokrovsk, ended a desperate effort by Ukraine to keep it running until the very last moment. As Ukraine’s last operational mine producing coking coal — an essential fuel for steel production — it was vital to the country’s steel industry and, ultimately, its war effort.

Miners who stayed despite the dangers were offered pay rises by Metinvest. To reach mining areas closest to the front, they had to walk through miles of tunnels protecting them from attacks. Shelling caused frequent blackouts, trapping them underground for hours.

“There is constant shelling, and it’s very close,” Maksym Rastyahaev, the head of a mining unit, said in a phone call after a shift at the mine shortly before Christmas. “Only the most resilient workers have remained.”

Now, the mine’s closure is expected to send shock waves through the economy. Steel production is projected to drop by more than half, from 7.5 million tons this year to less than 3 million next year, according to Oleksandr Kalenkov, head of Ukraine’s steel makers’ association. The fallout will affect trade — metal and steel products were Ukraine’s second-largest export last year — reduce tax revenues and strip the military of essential materials for armor production.

“The impact, in all its aspects, is tremendous,” Mr. Kalenkov said.

The mine near Pokrovsk is not the first to fall to Russia, whose forces have decimated much of eastern Ukraine’s industrial base. But its story is one of Ukrainian resilience: after scaling back operations following Russia’s full-scale invasion in 2022, coal production rebounded to 3.2 million tons in 2023, nearing prewar levels. That year, many residents returned to Pokrovsk, hopeful the tide of the war was turning in Ukraine’s favor.

The mine was an economic lifeline for the area. In 2023, Metinvest employed some 4,500 people at the facility, many of whom had spent most of their working lives there. “I’m a miner. I don’t know how to do anything else. All I know is how to mine coal,” said Yurii Nesterenko, 35, who had worked there for a decade.

The pay was good, and Metinvest’s mining facilities reflected a sense of care. On a visit this summer, the mine boasted flower beds, fountains and an Orthodox chapel adorned with gold icons and intricate ceilings, offering a quiet retreat for miners to pray.

By late summer 2024, however, the first signs of danger had appeared. Renewed Russian advances in the east had spurred a mobilization drive that drained the mine’s work force, prompting it to hire women to replace conscripted men. Even more concerning, the mine lay in the path of Russia’s push to flank Pokrovsk, a key military logistics hub.

“Everyone hoped Ukrainian soldiers would hold the line,” said Vyacheslav Dryha, an engineer who left the mine in the fall and is now in Kharkiv. Some employees began monitoring battlefield maps daily, tracking the Russian advance.

In late September, strikes on the mine killed four female workers in as many days. Two were at a laundry station, while the two others were waiting at a bus stop. The deaths sent a chill through the staff, prompting many to leave and join the flow of residents evacuating Pokrovsk. Russian forces were less than 10 miles away.

From then on, miners described strikes getting more and more frequent. Some opted to drive their own cars to the mine instead of taking the bus, to better evade drones that had appeared overhead. The mine’s shaft No. 3, located closest to the front, in the village of Pishchane, began coming under regular shelling.

In early December, when shaft No. 3 became too dangerous to use, miners switched to descending into the mine through another shaft farther west. From there, they faced a two-hour, six-mile trek through underground tunnels to reach the coal faces beneath shaft No. 3. To come back, they rode the conveyor belts transporting freshly extracted coal.

It was a perilous job. Power and ventilation systems sometimes broke down because of the shelling, forcing miners to evacuate. Yet, with the fighting raging above, they still felt safer underground, in the mine’s dim, nearly 2,000-foot-deep tunnels.

“The earth itself kind of protects you,” said Volodymyr Kohanevych, who maintained equipment at the mine.

Keeping the mine running as long as possible was critical for Metinvest, which relied on coking coal to smelt iron ore into steel at its factories further west. The steel is used to make rails for Ukraine’s railways, a transport lifeline during the war, as well as body armor and helmets for soldiers. Earlier this month, Metinvest launched production of protective armored plates for the U.S.-made Patriot air defense systems that protect Ukrainian skies.

“We’re like a second front, working for the victory,” Mr. Telegin said of the miners and steel workers.

But by mid-December, Mr. Telegin and his colleagues knew this second front was collapsing. Russian troops had advanced to within a mile of shaft No. 3, raising fears they might capture it and exploit its tunnels to outflank Ukrainian positions. In response, the miners, working with the military, began drilling holes beneath the shaft to place explosives, according to several workers.

A few days later, around Dec. 20, the shaft was blown up. “Everything collapsed, and now it’s all rock,” Mr. Telegin said.

A Metinvest manager, who requested anonymity because he was not authorized to speak, said explosives had also been placed in the facility’s two other shafts farther west, near the villages of Kotlyne and Udachne, which remain under Ukrainian control today. It is unclear if they have already been detonated.

From 7,000 tons of coal a day this summer, production fell to just over 2,000 tons by mid-December, the manager said. The strike on the electricity substation, on Christmas Eve, dealt the final blow: the mine shut down and production dropped to zero.

Mr. Kalenkov, the steel expert, said the mine’s closure put Ukraine in a precarious situation. Importing coking coal to make up for the loss will be costly and complicated by war-related logistical hurdles. He expects a strain on an already fragile economy, but also cutbacks in defense industry projects, such as the production of armor for Patriot systems.

“The loss of the mine definitely hinders Ukraine’s combat capabilities,” Mr. Kalenkov said.

Many of the roughly 1,000 miners who stayed until the end have now relocated to cities farther from the front such as Kyiv, Kharkiv and Dnipro. Some have already secured new jobs in factories, while others remain uncertain about their prospects.

Mr. Rastyahaev, 40, who spent half his life working at the mine, said it had been “very painful” to leave a place he had helped build and develop. As he spoke last week, he had yet to hear from his management about the mine’s future.

“Honestly,” he said, “I think it’s the end.”

Decades ago, Mozambique’s liberation party, Frelimo, easily attracted adoring crowds. The promise of salvation from Portuguese colonizers, and a life with jobs and housing for all, was an easy sell in a southern African nation that was suffering under racist rule.

But when Daniel Chapo of Frelimo became president on Wednesday, he assumed the leadership of a country more dissatisfied with his party than at any point during its 50 years of independence. Tens of thousands of people took to the street after the October election, which voters, international observers, opposition leaders and rights groups have roundly criticized as fraudulent.

The country of 33 million has been roiled by political chaos since the vote. And now, Frelimo’s grip on power is being tested like never before at a time when Mozambique faces urgent economic and social crises, analysts say. Two of the three opposition parties boycotted the inauguration and the opening of Parliament on Monday.

The anger among voters exploded into huge street protests in the past several months that led to clashes with the police. At least 300 people have been killed.

Mr. Chapo and his party had likely hoped that the inauguration on Wednesday would help move the country toward reconciliation and stability. But early signs suggested a difficult path toward unity.

The police quickly moved to disperse a few dozen peaceful protesters about two blocks from the inauguration in the capital, Maputo. The demonstrators fled when officers marched toward them with barking dogs lunging on leashes.

Officers fired several rounds of live ammunition to quell the demonstrations. But the show of force only angered the protesters, who yelled, “They won’t govern,” referring to Frelimo.

“We’re going to burn Mozambique,” said Angelina Chissano, one of the protesters in the capital on Wednesday.

Such demonstrations offered a glimpse of the new reality that Frelimo must contend with.

“Frelimo became used to seeing themselves as the chosen party,” said Gabriel Muthisse, a former top party official who remains an active member. “They believed that elections were only a formality for the people to confirm their leadership. Over the past five, 10 years, things are showing that that is false.”

After taking the oath of office, Mr. Chapo attempted to extend a hand to Mozambicans. He vowed to cut state spending by downsizing the government and reducing expensive perks that ministers receive. (The government is often criticized for spending lavishly on officials, while failing to meet many citizens’ basic needs.)

“I know many of us feel that leaders are distant, inaccessible and disconnected from the real concerns of the people,” Mr. Chapo said. “This will change.”

Mr. Chapo appeared to be taking a page out of his rival’s playbook. Venâncio Mondlane, the opposition leader, is seen by many to be the true champion of ordinary Mozambicans. The fiery populist claims to have won the election and has drawn a huge following, particularly from disaffected young voters.

When Mr. Mondlane, 50, returned to Mozambique last week after a self-imposed exile, the police responded with deadly force against supporters who took to the streets to greet him.

Mr. Mondlane has called for continued protests, though this week has not attracted the mass demonstrations that shut down the capital and other cities in previous months.

In an interview in Maputo, Mr. Mondlane said that he had communicated with Mr. Chapo through a mutual friend. He expressed hope that the president would negotiate a resolution to end the political crisis and accept reforms put forward by him in a recent proposal. On top of amending the constitution and overhauling government institutions, those reforms include building three million houses for poor Mozambicans and creating a half-billion-dollar fund for startups led by women and young people.

“You must give the people something very crucial and something tangible,” Mr. Mondlane said. “I don’t know if all the items that are in my proposal will be satisfied or not. But I think that we will begin a platform of dialogue.”

Protests were still needed, he added, because to ensure that reforms will happen, “you must put the government under pressure.”

Mr. Chapo, 48, emerged last year as Frelimo’s surprise presidential candidate. Unlike others in the party, he did not lobby for the nomination. He entered public office just 10 years ago, but came face to face with the country’s troubled political history long ago.

When he was 5, he said, his family was kidnapped by guerrilla forces fighting Frelimo during Mozambique’s 16-year civil war. A lawyer by training, he served as a provincial governor before running for the presidency for the first time last year as a member of Frelimo.

Branquinho João da Costa, a 43-year-old doctor living part time in Maputo, recalled his grade school days when the glory of Frelimo was drilled into him and his classmates through freedom songs. “It’s very difficult to be completely disconnected from Frelimo,” he said.

Many Mozambicans are now disgruntled with the party over accusations of corruption and its failure to address rising prices, which Mr. da Costa called “a new kind of slavery for the people.” He said the Frelimo of his childhood was more in touch with the party’s socialist roots, and that it was led then by officials who cared less about wealth and power.

“The real aim of Frelimo was serving people,” Mr. da Costa said. “Now many of them, they fight to get political positions just to steal from us.”

Frelimo no longer has the luxury of ignoring such criticism, some party members say. The past few months have been a warning, said Alsácia Sardinha, who was sworn in this week for her third term as a member of Parliament for Frelimo.

“We have to reinvent ourselves to respond to the demands of the people,” she said. That reinvention includes the party policing its own government against wrongdoing, she added.

Mr. Muthisse, the former Frelimo official, said that Parliament can no longer rubber stamp laws put forward by the president. The party needs to focus on reforming institutions, like the electoral commission and the courts, in order to regain public trust, he said.

That reform should be at the center of negotiations with the opposition, Mr. Muthisse said.

“Everybody has to bring ideas,” he said, “so that in the next elections, we all believe.”

When an Italian journalist was arrested in Iran in December, her boyfriend back home feared she might linger in prison for years. So, amid talk that Iran and Italy were negotiating a prisoner swap that involved the United States, he says, he decided to try to get a message to someone who might be in a position to help.

His name was Elon Musk.

Not only was Mr. Musk close to President-elect Donald J. Trump, a month before the journalist was detained, the tech billionaire had a secret meeting with the Iranian ambassador to the United Nations.

Last week, the journalist, Cecilia Sala, 29, was released from prison in Iran, and days later an Iranian engineer whom Italy had detained on an American extradition request was also freed. The engineer was accused of providing material for drones used in an Iranian-backed militia attack on a U.S. military base that killed three American servicemen.

Mr. Musk helped secure the release of Ms. Sala by reaching out to Iran’s ambassador to the U.N., Amir Saeid Iravani, according to two Iranian officials, one a senior diplomat at the Foreign Ministry, who are both familiar with the terms of the prisoner exchange. They asked that their names not be published because they were discussing a sensitive issue.

Neither Mr. Musk nor representatives of the Trump transition responded to repeated requests for comment.

How Mr. Musk, an increasingly active if uncredentialed player on the world stage since the Trump victory, came to take up the journalist’s cause remains unclear. He is close with Italy’s prime minister, Giorgia Meloni, who traveled to Mar-a-Lago, the Trump estate in Florida where Mr. Musk has been a regular, and met with the president-elect on Jan 4.

Ms. Meloni said at a news conference last week that Ms. Sala’s release was the result of a “complex work of diplomatic triangulation with Iran, and obviously also with the United States of America.” Her office and the Italian Foreign Ministry declined to comment for this article.

A senior Biden administration official said the American government had not been consulted about the negotiations, had not been given advance word about the releases, and disapproved of the deal. John Kirby, the spokesman for the National Security Council, said that the deal had been “an Italian decision from soup to nuts.”

At the news conference, Ms. Meloni said she did not know what part if any Mr. Musk had played in Ms. Sala’s release. “If he had a role, I am not aware of it,” she said.

The ambiguity highlights the unusual role Mr. Musk has been playing as he sits at Mr. Trump’s side, backing far-right parties in Europe even as he continues to promote his business interests abroad. Italy, for example, is currently exploring a potential deal with Mr. Musk’s SpaceX to provide secure communications for government and military officials through Starlink. And Ms. Meloni has been one of Mr. Musk’s ever-present European allies, hosting him at her party’s conference in 2023 and attending a gala with him last October.

By the time of Ms. Meloni’s trip to Mar-a-Lago, Ms. Sala’s boyfriend, Daniele Raineri, had already sought out Mr. Musk’s help through an intermediary, he said. In an interview, Mr. Raineri said that he had thought of him because he had read that there was “a channel between Musk and the Iranian diplomats, and that Musk also works in close contact with Trump.”

Mr. Raineri, who is also a journalist, said he fired off a message on Dec. 29 to an Italian computer expert and associate of Mr. Musk’s to ask if he could bring Ms. Sala’s case to the billionaire’s attention and seek his help.

The computer expert, Andrea Stroppa, said in an interview that Mr. Musk had acknowledged the request, but that he did not know whether he had become involved in the case.

In November, weeks before Ms. Sala was arrested, Mr. Musk met for more than an hour with the Iranian ambassador at the Iranian’s residence in Manhattan to discuss defusing tensions between Tehran and Washington as a new administration prepared to take power.

The Iranian officials interviewed for this article said that Mr. Musk contacted the ambassador again shortly after Prime Minister Meloni visited Mar-a-Lago.

The prisoner exchange between Iran and Italy then unfolded rapidly. Iran released Ms. Sala on Jan. 8, and four days later, Italy freed the Iranian engineer, Mohammad Abedini Najafabadi.

Mr. Abedini had been detained at the request of the U.S. Justice Department. A federal court in Massachusetts accused him of procuring drone technology for Iran that was used in the attack on the American base, which was in Jordan, in January 2024. The two Iranian officials said that when Mr. Musk spoke with the ambassador, he requested that Iran release Ms. Sala and reassured him that the United States would not pressure Italy to extradite the Iranian engineer.

Iran’s mission to the U.N. declined to comment on the recent engagement between Mr. Musk and the ambassador. In a statement, it said the two detainees had been released as a result of “bilateral cooperation and coordinated efforts of the political and intelligence sectors of Iran and Italy.”

All sides are being circumspect in public about what transpired, but to many observers the speedy release of the prisoners following the meeting between Mr. Trump and Ms. Meloni suggested that the topic had been discussed and a resolution was reached.

“The most likely reconstruction is that she got a signal of understanding from Trump that the incoming administration would not raise huge problems if it released Abedini,” said Ferdinando Nelli Feroci, a former Italian diplomat.

Italy detained Mr. Abedini in mid-December as he was transiting through Milan’s airport. Three days later, agents from the intelligence wing of the Revolutionary Guard raided Ms. Sala’s hotel room in Tehran and threw her into solitary confinement at Evin prison. She had traveled to Iran on a journalist visa.

A member of Iran’s Revolutionary Guards, and the two Iranian officials said the journalist had been arrested to pressure Italy to release Mr. Abedini. Iran has made the detention of foreign and dual nationals a centerpiece of its foreign policy for nearly five decades.

“It doesn’t matter who you are,” Shahin Modarres, a Rome-based expert on Iran and international security, said in a telephone interview. “You can be a journalist, a diplomat, a tourist.” He said, “What matters is if Iran thinks it can use you as leverage.”

Ms. Sala said in an interview that she had been held in a cell with no mattress and had slept on the floor with one blanket on top and another below. For weeks, she was denied her glasses, and throughout her detention she did not see a human face. She could hear the sound of other inmates crying and vomiting, she said, and was blindfolded and interrogated for hours nearly every day, she said.

What she feared the most, she said, was “that I would go insane.”

Mr. Raineri, her boyfriend, said that on Jan. 2, Ms. Meloni told Ms. Sala’s mother that within the next 48 hours there would be an important development.

Mr. Stroppa, the programmer, dropped hints on his account on X. He posted a portrayal of Mr. Trump, Ms. Meloni and Mr. Musk in ancient Roman attire on the day the prime minister visited Mar-a-Lago. And on the day Ms. Sala was released, he posted an AI-generated photo of Mr. Musk eating spaghetti with an Italian flag emoji.

Ms. Sala said she understood that Italy’s government did what it had to do to free her. “And whoever it was they needed to talk to, they talked to,” she said.

Ryan Mac and Mattathias Schwartz contributed reporting.

As Panama’s president laid a wreath to honor those who died protesting the American occupation 60 years ago, the ceremony attendees were resolute.

The commemoration this month came just days after President-elect Donald J. Trump falsely claimed China was controlling the Panama Canal and suggested he could use military force to retake the waterway.

The threat rippled through a country still haunted by the events of 1964, when students trying to plant the Panamanian flag in the U.S.-occupied canal zone were met with deadly force.

“My brother did not die for nothing,” said Carlos E. Bonilla Cacó, whose brother was killed in the demonstrations that sparked the movement leading Panamanians to regain sovereignty.

The country’s leader agreed.

In the foothill near the Panama Canal Authority’s office, President José Raúl Mulino was firm. “The canal is and will continue to be Panamanian,” he said.

The statement directly challenged Mr. Trump, who some analysts say is only posturing to press Panama to lower fees for American goods traversing the canal, a subject he has recently railed against.

But former American officials warn that he may alienate Panama at a time when China is trying to woo the country as an ally and expand its influence in Latin America.

“Trump’s saber rattling could dampen the Panamanian government’s desire to broaden the relationship with the U.S. economically,” said Ramon Escobar, who until September served on the National Security Council and is currently the managing director at Actum, a global consultancy firm.

He “may end up pushing them away at a time when there is a real opportunity to get Panama back into our orbit,” Mr. Escobar said.

The canal was constructed by the United States in the early 20th century, but Panama took back full control in 1999 and has since operated the waterway through the Panama Canal Authority.

Today, Panama holds special strategic significance for China because of the canal, but Beijing has been working to expand its influence in Latin America, and among developing countries more broadly. It has portrayed itself as an alternative to what it calls American hegemony and bullying, casting itself as a more sympathetic, fellow developing country.

And with significant investments in port construction worldwide, China is positioning itself to influence global commerce and monitor international activities.

Specifically, U.S. officials have grown increasingly concerned about two seaports at each end of the Panama Canal, which have been operated for decades by CK Hutchison Holdings, a company based in Hong Kong.

While CK Hutchison is a publicly listed conglomerate whose largest owner is a Hong Kong billionaire family, Beijing could still use its national security laws to force the company to assist in intelligence-gathering or military operations.

Panamanian officials argue, however, that China doesn’t pose a risk. The canal is open to the public, they say, and any Chinese interference would be visibly obvious.

“Anyone can use a satellite to see what is going in and out of the port,” Ilya Espino de Marotta, the deputy administrator of the Panama Canal, said in an interview last week. “The canal runs through the country, along national roads and is visible to the public.”

During his first administration, Mr. Trump did bring up the Panama Canal internally, indicating that he sees the waterway as unfinished business, said John Feeley, who served as U.S. ambassador to Panama from 2015 until 2018.

In June 2017, Mr. Trump met with the Panamanian president at the time, Juan Carlos Varela, and complained that the U.S. Navy was paying too much to traverse the canal — about $1 million annually, Mr. Feeley said. (That cost is so minuscule it would be akin to a rounding error in the Pentagon’s budget, analysts say.)

But Mr. Trump never brought up China’s presence or supposed influence over the canal even though just weeks previously Panama had broken off relations with Taiwan and aligned with Beijing, said Mr. Feeley, who attended the White House meeting between the leaders.

The former ambassador said he tried to get the White House to focus on China’s rising influence in Panama, but the issue never grew to a level of serious alarm.

At the time, China was promising to invest in big-ticket infrastructure items in Panama, including a canal bridge, as part of its Belt and Road Initiative. Through the initiative Beijing has increased its influence globally by investing in seaports, roads and trains from Kenya to Sri Lanka and, most recently, Latin America. Critics say Beijing uses the program to saddle foreign governments with failing projects or unsustainable debt in order to wield China’s leverage.

Mr. Feeley said he tried to get American companies to bid on such projects to counter China. But the U.S. Embassy in Panama City never got the White House’s backing to persuade American companies to bid, he said.

“It’s not that we are losing to China in Latin America; in most cases we aren’t even showing up to the commercial battlefield,” Mr. Feeley said.

Latin American governments like Panama’s have complained that when they put out bids for expensive infrastructure projects, the United States is often absent, forcing them to rely on others from Europe to China to get the work done.

“The U.S. isn’t bidding on big infrastructure projects here, but China is,” said Giulia de Sanctis, the president of the Panamanian Association of Business Executives. “Are we supposed to tell them now: ‘It’s time to get out of Panama; Trump doesn’t like you.’ Would anyone feel safe investing here then?”

The Panama Canal Authority has said that while the United States built the canal for military purposes, the Panamanians developed it into a major hub of global trade.

Once the U.S. military handed it over, the authority invested more than $5 billion to widen the waterway and accommodate the giant cargo ships that travel from the United States to East Asia, its most popular route.

“If it wasn’t for our investment, the canal would be irrelevant on the scale of global trade,” said Ms. Espino de Marotta.

“Our neutrality is our greatest business asset, and it enables us to be a route for global commerce,” she said. At the Atlantic entrance of the canal, three ports are separately operated by companies based in Hong Kong, Taiwan and the United States, she said.

“These ports have been managed by Hong Kong since 1997, throughout Trump’s first administration,” she added. “Trump never said a thing about it then, so why now?”

Some Panamanians are reluctant to allow China to invest further in the country. Although Mr. Varela shifted Panama’s diplomatic recognition to China from Taiwan and entered into several business agreements with Beijing, subsequent governments have sought to scale back these commitments.

Ramón Martínez, who served as the minister of commerce after Mr. Varela stepped down, expressed his discomfort with the political and economic agreements made by the earlier administration with China. He said he halted a free-trade agreement with China that was under negotiation. The bridge over the canal that China pledged to build was also paused.

Mr. Martínez emphasized that for Panama, its most important ally will always be the United States.

Last week, hundreds of tourists gathered on a terrace at the Miraflores Visitors Center, giving them a bird’s-eye view of the Panama Canal. They waved as a towering cruise ship squeezed its way through the canal.

“At first it made me laugh, the insanity of it all,” said Jacqueline Williams of Mr. Trump’s threats against Panama as she waved to a passing cruise ship. The 67-year-old nonprofit educator was visiting the canal from New York City.

“But then you think: This is a guy who idolizes Putin,” she said, referring to the Russian president. “Trump said on the campaign trail he wanted to restore peace to the world, but now he is threatening military expansionism.”

Alex E. Hernández contributed reporting from Panama City, Vivian Wang from Beijing and Emiliano Rodríguez Mega from Mexico City.

Poland’s prime minister appeared on Wednesday to confirm the conclusions of Western intelligence officials who had warned of a Russian plot to blow up cargo aircraft over Western countries.

“I can only confirm that Russia planned acts of air terror, not just against Poland but against airlines across the globe,” the prime minister, Donald Tusk, said during a meeting with Ukraine’s president, Volodymyr Zelensky.

Mr. Tusk did not elaborate, and it was unclear whether officials believed that Moscow was continuing to actively plan such an action.

Officials first became aware of the plot over the summer, when incendiary devices placed at shipping hubs in Britain and Germany ignited fires that caused minimal damage. In November, four Western officials briefed on intelligence about the operation said the fires had been part of a test of security measures carried out by Russia’s military intelligence service, known as the GRU.

The ultimate goal of the plot was not known, but intelligence agencies started an investigation into whether the intent was to destroy planes on American or European runways, or even blow up an aircraft midair.

By the fall, the White House became so concerned that President Biden ordered his national security adviser and the C.I.A. director to warn top aides of Russia’s president, Vladimir V. Putin, that such plotting could provoke a severe reaction from the United States. Any acts of sabotage that caused mass casualties would represent a serious escalation of conflict between Moscow and Washington, and the United States would hold Russia responsible for “enabling terrorism,” a senior official told The New York Times.

While the Kremlin has denied that its agents engage in sabotage, Western officials say Moscow has ordered its intelligence services to find ways to bring the war in Ukraine, soon to enter its fourth year, to Europe and the United States.

Many of the sabotage plots attributed to Russia appear amateurish, perhaps intended more to annoy than to terrorize. In December, Estonian authorities released details about a gang of GRU agents paid to break the windows of the interior minister’s car and deface World War II monuments, and in France Russian agents have been linked to antisemitic graffiti spray painted on walls.

But other episodes have been more sinister. Fires have broken out at arms factories supplying weapons to Ukraine as well as aboard buses and at shopping malls. And critical telecommunications cables crossing the Baltic Sea have been cut, though attributing these definitively to one country has been difficult. Last year, two assassins who were believed to have ties to Russia killed a Russian defector in southern Spain.

The sabotage campaign, officials said, is being waged almost exclusively by the GRU, an agency that has carried out sabotage and assassination operations in Europe since before Mr. Putin’s 2022 invasion of Ukraine. Most notably, it was operatives from the GRU who used a highly potent nerve agent in the attempted assassination of Sergei Skripal, a GRU turncoat who was living in Britain.

After Russia’s full-scale invasion of Ukraine, the GRU’s activities in Europe abated somewhat as European countries expelled operatives and limited travel for Russians. But in the past year, the agency has figured out ways to restore its operations. Officials say that many acts of sabotage are carried out by hired proxies, sometimes recruited over the internet. That is one reason the operations have so far achieved limited results. But officials worry that recruiting people over the internet to commit such operations also increases the risk of dangerous and potentially deadly mistakes.

“The GRU in particular is on a sustained mission to generate mayhem on British and European streets,” Ken McCallum, the director general of Britain’s Mi5, the country’s domestic intelligence service, warned in rare public remarks last fall. “We’ve seen arson, sabotage and more. Dangerous actions conducted with increasing recklessness.”