“These actions were taken to protect freedom of navigation and make international waters safer and more secure for U.S., coalition, and merchant vessels,” the post said.

The Houthi-affiliated al-Masirah TV reported four strikes on Sanaa, the capital of Yemen, seven on the port city of Hodeidah and at least one strike on Dhamar, south of the capital.

The attack on Sanaa came as the Houthis and their supporters were holding their weekly “million-man march” protest, which this week was focused on Israel’s killing of Hezbollah leader Hassan Nasrallah in an airstrike near Beirut, Lebanon, last Friday.

The Houthi-run Yemen News Agency, SABA, reported that Hashem Sharaf al-Din, a Houthi official, said that he considered the strikes “a desperate attempt” to intimidate the Yemeni people and he vowed not to be deterred by them.

But the Houthi attacks on commercial vessels have increasingly drawn the ire of international actors and condemnation by diplomats. The Red Sea is a key trade route between Asia, Europe and the Middle East. Since the strikes began, many vessels have been forced to reroute. Those that have not have sometimes paid severe consequences.

Ships have been hit and sustained damage, and some sailors have been abducted and held captive for many months, while others have died or been injured in the Houthi attacks. In August, a Houthi strike on a Greek oil tanker threatened to devolve into an environmental disaster as the burning ship remained at sea for weeks, with militia members threatening tugboats attempting to salvage the vessel. The ship was towed to safety in mid-September.

The attacks on commercial shipping have been met with counter strikes by the United States military and British troops before. Between January and May, the two countries’ militaries conducted at least five joint strikes against the Houthis in response to the attacks on shipping.

United States Central Command regularly announces actions against the militant group. In August, after the Houthis said they targeted American warships, the U.S. military struck back. Last week, the Houthis made a similar claim, and now appear to have drawn the same response.

The latest strikes by the United States come as tensions in the Middle East have risen significantly following Israel’s killing of Mr. Nasrallah, its expanded operations against Hezbollah in Lebanon and an escalating conflict with Iran, which launched a salvo of about 200 missiles at Israel on Tuesday in retaliation for the assassinations of some of its proxy groups’ leaders.

On Sunday, the Israeli military also struck in Yemen in response to several recent Houthi missile strikes targeting Israel.

In Mr. Biden’s first appearance at the podium of the briefing room since taking office, he faced a flurry of questions about concerns for a broader war in the Middle East, his relationship with Prime Minister Benjamin Netanyahu of Israel and what actions the United States may take against Iran after it fired some 200 ballistic missiles at Israel earlier this week.

Asked whether Mr. Netanyahu was refusing to agree to a diplomatic deal for a cease-fire — something Mr. Biden has repeatedly called for — to influence the results of the U.S. election, Mr. Biden asserted he has supported Israel more than any other American president.

“And I think Bibi should remember that,” Mr. Biden said, referring to the Israeli leader by a nickname. “Whether he’s trying to influence the election, I don’t know, but I’m not counting on that.”

Mr. Biden said his administration was considering imposing sanctions against Iran and was still communicating with Mr. Netanyahu’s team about what retaliatory steps Israel might take. Mr. Biden said he was not “seeking” to immediately speak to Mr. Netanyahu but expected to speak with him once Israel makes a decision about how it will respond to this week’s attack by Iran.

“I’m assuming when they make their judgment about how they’re going to respond, we will then have a discussion,” Mr. Biden said, emphasizing that his team was in constant contact with Mr. Netanyahu’s team.

“They are trying to figure out — this is high holidays as well — they’re not going to make a decision immediately,” Mr. Biden added. “So we’ll wait and see when they want to talk.”

Despite defending Israel’s right to defend itself, Mr. Biden also issued words of caution.

“The Israelis have every right to respond to the vicious attacks on them, not just from the Iranians but from everyone from Hezbollah to Houthis,” Mr. Biden said. “But the fact is they have to be very much more careful about dealing with civilian casualties.”

He added he was focused on working with allies to prevent a broader war in the region, but “when you have proxies as irrational as Hezbollah and the Houthis, it’s a hard thing to determine.”

What was clear from the twisted mangles of concrete and destroyed buildings across the Hezbollah stronghold of the Dahiya, along with Israel’s widening ground invasion in the south, is that Israel is determined to take the fight against Hezbollah to a new scale. It’s doing so not just in the south, where its ground invasion is seeking to halt Hezbollah’s rocket fire into northern Israel, but also with its systematic targeting of Hezbollah’s remaining leadership, whose movements Israeli intelligence apparently still track.

Many people in Lebanon and the broader Middle East had long feared that such a war was coming, even before the Hamas-led Oct. 7 attacks on Israel. Hezbollah began firing on northern Israel soon after in solidarity with Hamas in Gaza. Hezbollah last fought an inconclusive war with Israel in 2006, and, given Iran’s support for Hezbollah, concern had built over time that they would soon be at war again.

After nearly a year of tit-for-tat strikes, as both groups tested the tolerance of the other side, Israel dramatically escalated the confrontation.

Three weeks ago, Israel detonated thousands of Hezbollah’s pagers and walkie-talkies, killing scores of people and injuring thousands. Last Friday, Mr. Nasrallah was assassinated. And overnight on Thursday came the gigantic attack in which Israel tried to kill Mr. Safeiddine, whose fate remains unclear.

The fighting has now spread far outside of the area along the Lebanon-Israel border where the warring parties initially sought to keep it contained. Israel has sent ground troops tasked with destroying Hezbollah’s military infrastructure into southern Lebanon, its first such invasion since 2006. Nearly a dozen of its soldiers have been killed in clashes there, including two killed in northern Israel that the military announced on Friday.

Israel’s airstrikes — which it says target Hezbollah’s munitions, bases and commanders — regularly kill civilians, bring down buildings and send up huge clouds of smoke in and around Beirut and elsewhere in the country. One strike on Friday left a large crater near a border crossing with Syria, forcing people fleeing from one war-torn country to another to carry their possessions around its rim.

Hezbollah, although battered by Israel’s recent attacks, still fires barrages of rockets over the border, as well as missiles that reach deep inside Israel and send people running for shelters.

Israeli leaders now say they can no longer tolerate the threat that Hezbollah poses on their northern border and that the group must be pushed back so that the 60,000 Israelis who have fled their homes in the country’s north can return.

Hezbollah, which the United States considers a terrorist organization, says it will keep fighting until Israel’s attacks in Gaza cease and that it must defend Lebanon from Israeli aggression. Hundreds of thousands of Lebanese have fled their homes, including many from southern villages that Israel has largely destroyed.

Many Lebanese resent Hezbollah, whose military activities are outside of the state and not subject to any oversight, for dragging the country into a new war for the sake of Hamas.

But with Lebanon’s other political parties in disarray and the country’s economy suffering from a profound collapse, there are few other forces they can turn to for protection and to guide the country out of the spreading war.

Mr. Araghchi also appeared eager to convey Iran’s readiness to support a deal involving a joint cease-fire in Lebanon and in Gaza — even as Iran’s supreme leader, Ayatollah Ali Khamenei, expressed Iran’s readiness to fight Israel if the Islamic Republic is attacked again. Mr. Khamenei made his comments at Friday prayers in Tehran.

The twin images of diplomacy and defiance underscored Iran’s difficult position as it endeavors to assert itself but also limit damage to its land and people.

Mr. Araghchi described his discussion with Najib Mikati, Lebanon’s caretaker prime minister, as involving “very good negotiations and consultations,” according to Iranian Press TV, a government channel.

In a news conference he elaborated, saying that: “Iran supports the efforts for a cease-fire, provided that first, the rights of the Lebanese people are respected and it is accepted by the resistance, and second, it comes simultaneously with a cease-fire in Gaza,” according to the official state Islamic Republic News Agency.

The “resistance” is shorthand for the armed groups allied with Iran in countries across the Middle East, most importantly, in this context, Hezbollah.

While Mr. Araghchi raised the idea of a cease-fire, it is hard to imagine such a deal in the near-term because with Israel’s fatal attack on Hezbollah leader Hassan Nasrallah a week ago, hostilities have only spiraled. Mr. Araghchi’s trip to Lebanon came as fears mounted that Israel could counterattack Iran soon in retribution for Iran’s attack Tuesday on Israel, which was in retribution for the killing of Mr. Nasrallah and leaders of other militant groups allied with Iran.

Israel’s targets in Lebanon — it has bombed the country almost daily since Mr. Nasrallah’s assassination — have been Hezbollah leaders and their weapon stockpiles. However, the bombing has also killed civilians and put to flight more than a million Lebanese, who are fearful they will be caught in the crossfire, according to the Lebanese government.

Hezbollah is a Shiite Muslim militant group formed in the 1980s during the chaos of Lebanon’s civil war with the guidance of Iran. The intent was that it would fight the Israeli occupation in Lebanon and support the struggle of Palestinians in Israel. Since then, Hezbollah has become a powerful political force in Lebanon as well as a military one.

In a tweet on the platform X, Mr. Araghchi wrote: “I am in Beirut—alongside members of our Parliament and Red Crescent Society—to make clear that Iran will ALWAYS stand with people of Lebanon.” He called on other regional governments “to also display steadfastness in their support for Lebanon, especially amid onslaught by the Israeli regime.”

According to Iran’s state run Press TV, the foreign minister brought food and medicine with him for distribution to displaced Lebanese people.

At Thursday’s meetings in Doha, both Mr. Araghchi and Mr. Pezeshkian appeared eager to show their alliance with Gulf countries, even as some Iran-linked groups in Iraq have threatened to attack the oil and gas assets of the United Arab Emirates because of their relationship with Israel.

Publicly, however, they focused on their ties to their Arab neighbors. “Our neighbors are our priority,” said Mr. Araghchi in his tweet from Doha, adding “Dialogue is a must.”

Many people have simply fled the city, deeming it, after two weeks of intense bombardment, unlivable.

“When will this end?” the 7-year-old daughter of Farah Choucair, an economist who spent 14 years working for the United Nations, asked her mother last week.

For the child, the pounding Israeli strikes are a flashback to the deadly Beirut port blast, which ripped through the Lebanese capital just over four years ago and destroyed entire neighborhoods. Ms. Choucair, who now works for a media technology company, said it took years of psychological support for her to process the trauma, but her daughter never did.

“I don’t think she ever recovered,” she said of her daughter.

For many in Beirut, the continuing conflict is just one in a long line of human catastrophes. The city’s bullet-ridden apartment buildings serve as a daily reminder of Lebanon’s bloody 15-year civil war, which ended in 1990. A crippling economic collapse that struck decades later has left much of the country in poverty, and residents are still grappling with chronic power cuts even as the capital is bombarded.

Beirut and its surrounding neighborhoods have been pounded by Israeli airstrikes targeting Hezbollah and its leaders for the past two weeks, reducing sections of the city to ruins. Just months ago, an Israeli strike in the heart of the city was an abrupt turn of events that escalated the conflict. Now, it is fast becoming the norm, punctuating bedtimes, family dinners and phone calls with friends.

Many residents say they loathe the stereotype that the Lebanese are resilient.

“I wish sometimes that we could just sit and cry our eyes out and not know what to do, but we always know what to do — what to pack, what we need,” said Ms. Choucair. “It has nothing to do with resilience or any positive trait. It’s a natural survival mode that we have been trained to automate.”

She added: “This is how it is living in Beirut. It will never change. I am 41. It has been like this for as long as I remember.”

Many apartments now lie vacant in Beirut, a once-bustling Mediterranean city and home to 2.5 million people. Those that had the means have fled up the coast or into the surrounding hills, but this has done little to ease their growing fears. The distant thump of Israeli airstrikes seems to draw closer with each passing day. Nights, too, are spent fretting over whether a sound was just a neighbor’s slamming door — or something more.

“All my dreams are about bombs,” said Heba Jundi, 36, who was staying at a friend’s house in the mountains above Beirut with her cat, Benji.

“Some nights I go to bed, I close my eyes, but I don’t allow myself to sleep,” said Ms. Jundi. “I’m telling myself that I’m waiting for the bomb to happen, and that I’m going to hear it any second now. We are all waiting for this to stop, but at the same time we know it is not going to stop, and we just have no clue or understanding of where this is going to go.”

Like so many others, she had begun taking anti-anxiety medication to deal with the stress, but said it was having little effect.

“I don’t know how much more the city can take,” Ms. Jundi said, “and I don’t think anyone wants to find out.”

The monitoring group said that the strikes were supported by planes believed to be Israeli and that Syrian air defenses and Russian forces were “confronting” the missiles for over 40 minutes. Rybar said that some of Israel’s cruise missiles were shot down by Russian antiaircraft fire from Russia’s nearby base but that others hit a warehouse used by Syrian and Iranian forces.

The Israeli military, the Syrian government and the Russian Ministry of Defense did not respond to requests for comment.

The reported attack raises the possibility that Russia — an Iranian ally that has sought to distance itself from Iran’s conflict with Israel — could become ensnared in the widening conflict in the Middle East. Russia intervened in Syria’s civil war in 2015 alongside Iran in support of President Bashar al-Assad, and helped him maintain power with brutal bombardments against rebel-held cities.

Though Russia decreased its footprint in Syria after its full-scale invasion of Ukraine in 2022, according to officials based in the Middle East, it maintains a sizable presence in the country, including at the Hmeimim air base near the city of Jableh.

Video footage and photographs posted online from the city of Jableh and verified by The New York Times show an explosion in the direction of the air base. The images were taken from a spot roughly three miles from the base, according to the Times analysis.

The reports of the strike came amid major Israeli military operations on Thursday on multiple fronts against Iranian-backed groups in Gaza and Lebanon and militants in the West Bank, most of which are part of a network that Iran calls the Axis of Resistance. That network also includes the Syrian government, which Israel has long accused of helping funnel arms to Hezbollah through its shared border with Lebanon.

The reported attack came soon after the arrival of an Iranian plane belonging to the Qeshm Fars airline, according to a news site aligned with the Syrian opposition that is headquartered in Turkey. The United States imposed sanctions on the airline in 2019, citing its regular flights to Damascus “delivering cargo, including weapons shipments” on behalf of the Islamic Revolutionary Guards Corps. Iran’s Revolutionary Guard provides arms to its Axis of Resistance network, including Hezbollah.

Flightradar24, a flight tracking website, showed that a Qeshm Fars flight took off from Latakia soon after 5 p.m. local time on Tuesday and landed about two hours later in Tehran.

After Israel ramped up its war with Hezbollah in Lebanon over the last two weeks, U.S. and Israeli officials said that Israel had eliminated about half of the Lebanese group’s formidable stockpile of rockets and missiles. Israel has sought to prevent the group from rearming with support of its backer, Iran.

On Thursday, a spokesman for the Israeli military again accused Hezbollah of bringing in Iranian arms via Syria, as social media chatter about the reported strike multiplied.

Charles Lister, the director of Middle East Institute’s Syria and counterterrorism programs, said on Thursday that, “By itself, this is just another Israeli strike on another weapons shipment in Syria, but the proximity to Hmeimim is rare.”

“By striking so close to Russia’s flagship base,” he added, “Israel may also be sending a signal that in such zero-sum circumstances, anything is deemed a legitimate target and an acceptable risk.”

The strike set off huge explosions and left a ruined landscape of jagged concrete, twisted metal and smoldering debris in the Dahiya, a densely populated area where an Israeli strike on Sept. 28 killed Hezbollah’s longtime leader, Hassan Nasrallah.

Above is a look at who has been killed and targeted among Hezbollah’s leadership.

“Our family and the entire camp is already devastated,” said Anas Kharyoush, a cousin of the children’s mother, 28-year-old Saja Abu Zahra, referring to the neighborhood’s origin as a refugee camp for Palestinians displaced from their homes by the wars surrounding Israel’s establishment. “They are not the first martyrs in our family, and this is not the first airstrike in our neighborhood, but it’s the most devastating.”

The explosion was so fierce that the remains of those killed had to be gathered in blankets and sheets and taken to a hospital for bereft family members to identify, according to residents and videos of the aftermath. And the search for the missing continued.

“Mothers are desperate to know about their children, and families are still looking for their loved ones,” said Diala Hadaydah, a paramedic who lives in the neighborhood, who rushed to the scene moments after the strike.

The Israeli military did not respond to questions about the number of civilians killed in Thursday’s strike.

The strike in the densely packed area came amid increasingly deadly Israeli raids on Palestinian towns and cities across the Israeli-occupied West Bank, in what the military labels counterterrorism operations.

Tulkarm, which has a history of armed resistance against the nearly six-decade Israeli occupation of the West Bank, has been the frequent target of such raids. For more than nine days, starting in late August, Israeli bulldozers ripped through roads, infrastructure and businesses there, as well as in nearby Jenin.

Palestinians say they are terrified in their own homes, fearful of onslaughts from the ground — from tanks, armored vehicles or more bulldozers — and from the sky. The Israeli military has said the raids are an effort to crack down on Palestinian armed groups and combat rising attacks against Israelis and settlements.

Israeli settlements are considered illegal under international law but have continued to expand, threatening Palestinian livelihoods in cities, towns and farming villages.

Violence in the West Bank has been increasing since the war began in Gaza last Oct. 7, but the toll has been far higher among Palestinians. As one gauge, a United Nations report in mid-September, counting conflict fatalities from January 2023 onward, put Israeli fatalities at 41 and Palestinian fatalities at 722.

In the strike on Tulkarm on Thursday, witnesses said that an Israeli warplane fired at least one missile at the cafe while it was occupied by civilians. The use of a warplane there was unusual. Though Israel has increasingly been conducting once-rare airstrikes in the West Bank since the Oct. 7 Hamas-led attack on Israel, they have usually been carried out by armed drones.

Ms. Hadaydah, the paramedic, said the sound of the explosion was unlike anything she had ever heard before. She rushed to the scene and saw the scattered remains of body parts, burned beyond recognition. Ms. Hadaydah said only five bodies were intact.

“I saw teeth, I saw skin, I saw bodies hanging from electricity cables,” Ms. Hadaydah said. “It looked just like Gaza.”

In his sermon, Mr. Khamenei, donning a Palestinian checkered kaffiyeh, praised Hamas’s Oct. 7 attack on Israel nearly a year ago as a “logical, just and internationally legal action” because of Israel’s long occupation of Palestinian territories. He referred to Israel as “a rabid dog,” “blood thirsty,” and “wolf like,” and said that “any strike on the Zionist regime is a service to humanity.”

He pledged support for the network of regional militias Iran backs that is known as the “axis of resistance,” which includes Hamas and Hezbollah, and which has taken significant hits from Israeli strikes in recent weeks. And he said that Iran would continue to support the Palestinians and Lebanese and called for pan-Muslim unity to stand against Israel and the United States, which he said was an accomplice in what he called Israel’s military crimes.

“The Islamic Republic will fulfill all its duty in this regard with force, determination and strength,” Mr. Khamenei said. “We will not rush nor delay.”

If necessary in the future, he added, Iran would respond again, as it had done days earlier by launching ballistic missiles at Israel.

Mr. Khamenei’s appearance in person at the prayers, despite security concerns, signaled the significance of the moment, as anxiety has mounted that Israel and Iran appear prepared to risk all-out conflict.

Sina Azodi, an adjunct professor at George Washington University and an expert on Iran’s national security, said that Mr. Khamenei’s message “was one of defiance, solidarity with resistance groups and the Arab public and to shore up domestic support for a potential conflict with Israel.” He added, “He is sending a signaling to abroad that Iran is not going to take any irrational actions or escalate but will respond to potential attacks.”

State television showed tens of thousands of supporters packing the sprawling arena — men sitting separately from women — and spilling into the streets of central Tehran. They waved Hezbollah, Lebanese and Palestinian flags and held up posters of Mr. Nasrallah. Some men wore yellow Hezbollah headbands.

One woman, who was shrouded in a white cloth symbolizing martyrdom and attended the event with her family and toddler in tow, told state television that she came to deliver a message, “Since the enemy has threatened us, we are here to say we are not afraid of anything.”

Despite official rhetoric, in interviews, virtual town halls and social media posts, many Iranians said they were anxious about a war with Israel and that they do not want one.

Mr. Khamenei switched from Persian to Arabic to address Palestinians and people in Lebanon, which has been battered by Israeli strikes targeting Hezbollah. He defended Tuesday’s Iranian missile attack against Israel as “completely legal and legitimate.”

“What our armed forces did was the least punishment they could do” against Israel, he said, adding, “what is logical and rational will be done at the right time and will be done again in the future if necessary.”

Senior Iranian officials, including the new president Masoud Pezeshkian, the head of parliament and senior military commanders sat in the front row during the ceremony. Mr. Pezeshkian told reporters ahead of the event that the ceremony aimed to “project a show of unity, cohesion and power.”

On Tuesday, Iran fired nearly 200 missiles at Israel in retaliation for Mr. Nasrallah’s death and the recent killings of Hamas’s political leader, Ismail Haniyeh, and an Iranian commander, Iran’s Islamic Revolutionary Guards Corps said. Israel has said it would retaliate with strikes against Iran, sparking fears of a regional war.

In a series of attacks, Israel has aimed to reduce the military capabilities and dismantle the leadership of Hezbollah, a militia group backed by Iran and based in Lebanon. On Thursday night around midnight, Israel launched an intense barrage of airstrikes in a neighborhood south of Beirut in an effort to target Hashem Safieddine, Mr. Nasrallah’s presumed successor, according to three Israeli officials.It is rare for Mr.Khamenei to lead Friday prayers and deliver the sermon, typically doing so only under extraordinary circumstances related to Iran’s national security. The last time was in 2020, after the United States killed Iran’s top general, Maj. Gen. Qassim Suleimani, in Iraq. Iran retaliated by firing ballistic missiles at an American base in Iraq.

Plans for an official funeral for Mr. Nasrallah have not been announced. It is not clear whether it is feasible for Hezbollah and what remains of its leadership to gather publicly, given Israel’s attacks.

Israel said on Friday that a separate airstrike the previous day had killed Mohammad Rashid Sakafi, who it identified as a commander responsible for Hezbollah’s telecommunications division. Hezbollah, the Lebanese militia and political party backed by Iran, did not immediately comment on the claim.

As Israeli warplanes pummeled the Beirut area, soldiers were waging a ground invasion in southern Lebanon targeting what military officials said were Hezbollah sites in the rugged border area.

New evacuation orders issued on Friday brought to 87 the total number of Lebanese communities whose residents Israel has told to leave. Many are to the north of a swath of southern Lebanon that was designated a buffer zone by a 2006 U.N. Security Council resolution after the last Israel-Hezbollah war.

Israeli fighter jets also struck near of Lebanon’s Masnaa border crossing with Syria, cutting off a road used by hundreds of thousands of people fleeing Lebanon, Bachir Khodr, the governor of the Baalbek-Hermel region, said on Friday.

The Israeli military said the area — which lies on the highway linking Beirut and Damascus near the geographic center of the country — also contained a two-mile-long tunnel that was the main route used by Hezbollah to bring weapons into Lebanon from Syria, another Iranian ally.

The Israeli airstrike left a crater in the road but people were still crossing into Syria on foot, Rula Amin, a spokeswoman for the U.N. refugee agency, told reporters by video link from Beirut on Friday. “It’s a testament to the fear and panic that is driving people to cross into Syria,” she said.

In Israel on Friday, air-raid sirens sounded across much of the north as Hezbollah continued to fire rockets at the region. Residents reported hearing loud explosions in the sky — possibly from air defenses intercepting rockets. Israel’s military said around 100 rockets had been launched as of early afternoon, but the authorities did not immediately report casualties or significant damage.

Euan Ward contributed reporting from Beirut, Lebanon, and Nick Cumming-Bruce from Geneva.