“We are following the threat from Iraq,” Admiral Hagari said, while declining to say if or how Israel might retaliate but saying it would do whatever was necessary to address the matter.

The Islamic Resistance in Iraq published a statement on social media on Wednesday, saying it had targeted Eilat with drones in support of the Lebanese and Palestinian people. Israel has been bombing the Gaza Strip and Lebanon in an effort to destroy Hamas and Hezbollah. Both armed groups are backed by Iran and dedicated to destroying Israel.

Earlier on Wednesday, the Iraqi group had said in a statement that it had also aimed drones at Israel’s Jordan Valley. The Israeli military reported that a drone fell in the desert early Wednesday, causing no injuries or damage, after sirens had sounded in Israel, near the border of Jordan.

The latest strikes from the Iran-backed group in Iraq highlight the expansive role of Iran in Israel’s current conflicts, and how quickly any escalation could draw in more regional players.

Hezbollah began launching missiles into Israel from Lebanon a day after Hamas led an attack on Israeli communities on Oct. 7 last year, killing 1,200 people and taking 250 hostage.

Similarly, the Houthi militia in Yemen, also supported by Iran, has been attacking vessels in the Red Sea since last year, disrupting commercial shipping and forcing international shippers to seek alternate routes. The Houthis have also said that they are acting in solidarity with Hamas in Gaza.

According to the State Department, Islamic Resistance in Iraq is a group that includes multiple “terrorist and militia groups” responsible for dozens of attacks on U.S. military personnel in Iraq and Syria. In August, a rocket attack targeting U.S. personnel housed at a base in Iraq’s western desert injured several American troops. It resembled previous strikes carried out by Iran-backed Iraqi armed groups, which have intensified their attacks after the war in Gaza began.

International diplomats have been scrambling to broker a cease-fire agreement between Israel and Hamas, in the hopes it will deter a wider war that could draw Iran directly into the conflict. Those talks have stalled in recent months, and the United States and others are now working on a proposal to cease hostilities between Israel and Hezbollah in Lebanon and address the war in Gaza.

The United States, which has designated Hamas, Hezbollah and members of the umbrella group Islamic Resistance in Iraq as terrorist organizations, has tried to cripple them by cutting off their funding. On Wednesday, the Treasury Department said it had sanctioned about a dozen individuals, businesses and vessels in connection with oil and gas sales for the Iranian Revolutionary Guard Corps and Hezbollah.

Iran relies heavily on illicit sales to fund its proxy groups and to pay for “destabilizing activities,” Bradley T. Smith of the Treasury Department said in a statement, adding that the United States “remains committed to disrupting the networks of shippers, brokers, and buyers that facilitate these schemes.”

Officials said there were indications that Israel and Lebanon were supportive of talks that might soon lead to a cease-fire, and Mr. Biden and Mr. Macron called for “immediate support” for the proposal by the two governments.

The proposal was endorsed by Australia, Canada, the European Union, France, Germany, Italy, Japan, Saudi Arabia, the United Arab Emirates and Qatar. In a statement, all of the signatories called for “an immediate 21-day cease-fire across the Lebanon-Israel border” to provide space for further negotiations.

Mr. Biden, arriving back in Washington from the United Nations General Assembly in New York, told reporters that “we were able to generate significant support from Europe, as well as the Arab nations.” He added: “It’s important the war does not widen. I’ll have more to say tomorrow.”

Two American officials said late Wednesday that they hoped a three-week cease-fire would allow time for a permanent end to the fighting between the two countries. They hinted that Israel and Lebanon had been supportive of the rapid-fire discussions over the previous 48 hours and might agree to the proposal soon.

One official said that diplomats have had conversations with both countries and were hopeful that representatives of their governments would accept the proposal for a cease-fire in “the coming hours.”

Hezbollah, a militant group that does not have the same accountability as a state institution in Lebanon, would not be formally asked to accept the proposal. But the officials, who spoke to reporters on the condition of anonymity because of the sensitivity of the negotiations, said that if Lebanon agreed to a cease-fire, its government would be expected to ensure that Hezbollah fighters adhered to it during the 21-day period.

They said a temporary pause in the fighting could provide “diplomatic space” that could help revive stalled negotiations over the fighting in Gaza between Hamas and Israel. Mr. Biden offered a three-step proposal in May to bring an end to the nearly yearlong war in Gaza, but it has stalled amid objections from both Israel and Hamas.

The proposal from nearly a dozen countries came after intense discussions between Secretary of State Antony J. Blinken and other diplomats on the sidelines of the U.N. General Assembly in New York, where leaders from around the globe are confronting the latest violence in the Middle East.

Jean-Noël Barrot, France’s minister for Europe and foreign affairs, told the U.N. Security Council during an emergency session on the crisis on Wednesday evening that neither country had yet signed on to the proposal after a of wave of fierce airstrikes by Israeli forces that have killed hundreds of people over the past week. But officials said they would try to persuade the two sides to agree to the proposal in the coming days.

Mr. Barrot said he was traveling to Beirut at the end of the week to work with Lebanese officials on supporting a cease-fire.

The immediate goal of the diplomatic effort is to reduce the chance that the deadliest week of fighting between Lebanon and Israel in years will draw the region into a wider conflict that kills many people and destabilizes the region.

But American officials also hope that stepping back from a war with Hezbollah would put pressure on Yahya Sinwar, Hamas’s leader, to agree to a deal that would end nearly a year of fighting in Gaza and lead to the release of the remaining hostages taken during the Oct. 7 attacks.

The push for an end to the fighting comes at what American officials describe as a dangerous new moment in the yearlong spiral of violence, with the possibility of a second front along the border with Lebanon that could draw much bigger players. Hezbollah is supported by Iran, which considers the group its most important proxy in the region.

“An all-out war is possible, but I think there’s also the opportunity — we’re still in play to have a settlement that can fundamentally change the whole region,” President Biden said during an appearance earlier on Wednesday on ABC’s “The View.”

The president is under intense pressure to avert that broader conflict, and the clock is ticking. There are 117 days left before Mr. Biden leaves office. He and his aides have been searching — so far unsuccessfully — for a negotiated solution to the violence that would help Mr. Biden burnish his legacy on the world stage.

Mr. Blinken has been shuttling back and forth this week between European and Arab delegations in New York for the U.N. General Assembly to try to clinch the temporary cease-fire, a U.S. official said, speaking on the condition of anonymity to discuss the closed-door diplomacy.

The efforts have focused on trying to get multiple nations across Europe and the Middle East to agree to the terms of a proposal that would then be presented to Israel and Hezbollah in Lebanon.

On Monday, Mr. Blinken raised the issue at dinner with top diplomats from the Group of 7 nations. He told them that the United States was working on a proposal and wanted to keep efforts coordinated, the official said.

Then on Wednesday morning, at a session with top diplomats of Gulf Arab nations, Mr. Blinken pulled aside Mohammed bin Abdulrahman Al Thani of Qatar and got his country’s agreement to support the proposal. At the end of that session, Mr. Blinken did the same with Faisal bin Farhad al-Saud, the foreign minister of Saudi Arabia.

Along with Amos Hochstein, the White House official who conducts diplomacy with Lebanon, Mr. Blinken met with the prime minister of Lebanon, Najib Mikati, on Wednesday. By Wednesday evening, the Biden administration had gotten multiple European and Arab nations on board with the proposed terms, and was ready to announce the proposal.

The new push represents the first time since Oct. 7 that the United States has sought to link the two conflicts involving Israel into a single diplomatic effort.

The logic, according to another official, who spoke on condition of anonymity to discuss sensitive diplomatic negotiations, is that Hamas has sought to sow regional discord and chaos since the moment of the Oct. 7 attacks by triggering a wider war. As long as Israel is caught in an escalating series of conflicts, officials believe, the leadership of Hamas will not be motivated to reach a deal.

That official said the United States believed that Mr. Sinwar would have less leverage over the situation if the fighting between Israel and Hezbollah stopped and could feel more pressure to agree to a cease-fire deal in Gaza.

The official cautioned that it remained uncertain whether Hassan Nasrallah, Hezbollah’s leader, or the Israeli government of Prime Minister Benjamin Netanyahu was prepared to agree to a halt in the fighting.

Some Israeli military officials have argued for months for a more aggressive response to Hezbollah’s attacks. On Wednesday, Lt. Gen. Herzi Halevi, the Israeli military chief of staff, hinted that a ground invasion in Lebanon was possible.

“You hear the jets overhead; we have been striking all day,” General Halevi told soldiers along Israel’s border with Lebanon. “This is both to prepare the ground for your possible entry and to continue degrading Hezbollah.”

Mr. Nasrallah pledged support for Hamas after the group killed about 1,200 people in a surprise attack last year in Israel. Hezbollah has repeatedly fired missiles and drones into northern Israel, forcing Israelis to flee their homes near the border.

One of the officials said it was unclear whether Hezbollah’s leader was willing to accept a cease-fire deal without seeing movement toward a similar deal in Gaza, which could complicate the effort.

The diplomacy is being conducted by the United States, with support from France. It comes a week after pagers and walkie-talkies used by Hezbollah fighters exploded across Lebanon, killing dozens of people and injuring thousands in an attack apparently orchestrated by Israel.

Israeli officials have not said Israel was responsible for the remote attacks, in which the communications devices were packed with explosives and remotely detonated. But a dozen current and former defense and intelligence officials who were briefed on the attacks said that Israel used shell companies to get into the supply chain and booby-trap the devices.

Zolan Kanno-Youngs contributed reporting.

The Israeli military was drawing up plans for a ground maneuver that would see soldiers “enter enemy territory, enter villages that Hezbollah has prepared as large military outposts,” General Halevi added.

It was not clear whether his remarks were saber-rattling or a realistic scenario being weighed by Israeli decision makers. In 2006, Israel invaded Lebanon as part of a 34-day war with Hezbollah, leading to deadly battles on the Iranian-backed militant group’s home turf.

“Your entry into those areas with force, your encounter with Hezbollah operatives, will show them what it means to face a professional, highly skilled and battle-experienced force,” General Halevi told the soldiers. “You go in, destroy the enemy there and decisively destroy their infrastructure.”

Israel has deployed additional soldiers and resources to the fight against Hezbollah as the battle between the two sides has rapidly escalated over the past week. On Wednesday, the Israeli military announced that two more brigades were being mobilized for “operational missions” along the northern front.

For now, Israeli officials have emphasized that they are focusing on an intensive aerial campaign against Hezbollah military sites. Sending Israeli forces into Lebanon could take an additional toll on Israel, which has been fighting Hamas on the ground in Gaza for months.

It would also raise bitter memories for the Lebanese people. Israeli forces occupied much of southern Lebanon for about two decades as part of a “security zone” intended to prevent cross-border attacks by militants. The occupation ended with Israel’s withdrawal in 2000.

Hezbollah began firing missiles and drones at Israel in solidarity with its Palestinian ally, Hamas, after the Gaza-based group led attacks in Israel on Oct. 7. The fighting has displaced roughly 60,000 Israelis and hundreds of thousands of Lebanese, according to authorities in both countries.

Nearly a year after the Oct. 7 attacks, Israeli officials face increasing domestic pressure to push Hezbollah away from the border. But while Hezbollah has sustained several blows over the past week, its leaders have vowed to press on until Israel ends its devastating war against Hamas in Gaza.

How big is Hezbollah?

The C.I.A. World Factbook estimated in 2024 that Hezbollah had 50,000 armed combatants, although it said that not all were full-time soldiers. That would make it one of the largest militia groups in the region, behind the Houthis, who operate in Yemen and who the C.I.A. estimated had 200,000 fighters in 2022. Hezbollah’s leader, Hassan Nasrallah, has said that his group has 100,000 trained fighters.

One of Hezbollah’s political objectives, however, is to present itself as a giant capable of going toe-to-toe with Israel, and so Mr. Nasrallah has an interest in maximizing and potentially inflating the group’s size and capability, according to experts. It even opened a museum in southern Lebanon to showcase its fight against Israel.

“It is in Hezbollah’s interest to engage in psychological warfare that amplifies its power and capacity in the face of the enemy,” said Lina Khatib, an associate in the Middle East and North Africa program at the Chatham House research group in London. She said in an interview that Israeli officials had also inflated Hezbollah’s strength to support the country’s recent attacks, some of the heaviest aerial assaults in modern warfare.

What about Hezbollah’s weapons?

Hezbollah has perhaps the largest arsenal of any armed group in the world, excluding governments, according to experts. Aside from machine guns, rocket-propelled grenade launchers and mortars, the C.I.A. said, Hezbollah possesses around 150,000 rockets and missiles of various types.

In the past two decades, Hezbollah has “developed elements of a more traditional statelike conventional military force and demonstrated considerable military capabilities,” the C.I.A. said. It sustained huge losses during a conflict with Israel in 2006, but emerged intact, and, since then, its weaponry has grown in size and sophistication, according to experts.

But estimates vary. A report in March by the Center for Strategic and International Studies, a research organization based in Washington, put the size of Hezbollah’s stockpile between 120,000 and 200,000 rockets and missiles and said they included guided ballistic missiles, short-range and midrange unguided ballistic missiles and short- and long-range unguided rockets.

“Because of Hezbollah’s close relationship with Iran, it is likely that Tehran would resupply Hezbollah quickly if it used this arsenal in a conflict with Israel,” the report said, adding that Iran’s relationships with Syria would facilitate the weapons pipeline.

One measure of Hezbollah’s strength is the weapons it has deployed against Israel in the past year. On Wednesday, Hezbollah said it had used a midrange missile in an attempt to strike the headquarters of Israel’s spy agency, Mossad, in Tel Aviv, a distance of around 70 miles.

The attack was an outlier, however. Hezbollah has launched more than a thousand attacks on northern Israel in the past year, using exploding drones, anti-tank missiles and short-range rockets that can carry around 44 pounds of explosives, according to an analysis on Tuesday by the Institute of National Security Studies at Tel Aviv University. Most have been intercepted by Israel’s missile defenses. One missile fired on Sunday hit a residential neighborhood in the city of Kiryat Bialik, which is around 17 miles south of the border. This appeared to have been its deepest strike to that point.

Hezbollah has also occasionally deployed a Burkan rocket, which has a range up to six miles and can carry a much bigger warhead, the report said.

Where does Hezbollah gets its weapons?

Ms. Khatib argued that Hezbollah relied on Iran for much of its stockpile, but this was also a constraint, given sanctions on Tehran. At the same time, she said, the group had developed its own program to modify and upgrade missiles, and had built a network of tunnels and bunkers in which to hide them.

Hezbollah has developed an arsenal specifically to counter Israel’s military strengths and also to strike critical infrastructure and cities in an attempt to sap the Israeli government’s resolve in the event of a ground invasion, according to Nicholas Blanford, a Beirut-based analyst with The Atlantic Council, a think tank based in Washington.

To do this, he said, the militant group has gotten weapons and other military technology, not just from Iran, but also from Syria and, indirectly, from Russia, as well as from the black market. But so far, Hezbollah has relied for the most part on legacy weapons such as Katyusha rockets and has not used its most advanced equipment, which includes missiles capable of hitting tanks and ships.

“The good stuff that they have, such as precision-guided missiles, those are being held in reserve,” Mr. Blanford said in an interview. “The day that Hezbollah starts using those is the day a relatively limited conflict will explode into a major war.”

What about longer-range missiles?

Hezbollah’s attacks in the past year have prompted Israel to order the evacuation of tens of thousands of people from northern Israel, but the group also has the capacity to target cities farther south.

The Institute of National Security Studies cited one missile in the group’s arsenal that had a range of around 130 miles and could carry a payload of more than 1,000 pounds. It described that missile, the Zelzal, as inaccurate, but said that Hezbollah could also use another type of missile, the Fateh-110, which is more advanced, precise and can exceed the Zelzal in range and payload.

Ms. Khatib said that Hezbollah would be loath to use its most powerful weapons in the present conflict and would most likely deploy them in the event of a full-scale regional war.

Many Lebanese are still taking stock of those lost on Monday, when Israeli strikes killed 558 people in a single day, according to Lebanon’s health ministry. The toll includes 50 children and 94 women.

Among them was Dina Darwiche, an employee of the United Nations refugee agency, UNHCR. Her body was found along with that of her youngest son after an Israeli missile hit the building where they lived in Lebanon’s eastern Bekaa region.

Friends wrote tributes to Ms. Darwiche on social media, many of them posting a selfie of her smiling and posing with the son who was killed with her. Others shared a video of a U.N. campaign she ran in previous years against gender-based violence.

“She had been dedicated to her humanitarian work with UNHCR for as long as I can remember,” her friend, Jasmin Diab, posted on the social media platform X. “I am broken. I am absolutely destroyed. I cannot breathe. When will the world let us breathe?!”

Israel and Hezbollah, an Iran-backed militia and political party with powerful sway over Lebanon, have been locked in near daily cross-border skirmishes since the Hamas-led Oct. 7 attacks. Hezbollah began launching rockets in a bid to push Israel toward a cease-fire in Hamas-controlled Gaza, where more than 40,000 have been killed.

But the tempo of those sporadic clashes, which forced tens of thousands of Lebanese and Israelis on either side of the border to flee their homes, reached a new level with Israel’s strikes in recent days.

Military experts have called Israel’s latest campaign one of the most intense air raids in modern warfare.

Israeli officials argue that the strikes are not targeting civilians, and they point to evacuation orders for targeted areas as proof. But rights groups counter that Israel doesn’t specify regions to evacuate but warns people to stay away from places where Hezbollah is hiding weapons, an assessment that is difficult to impossible for civilians to assess.

Lebanon’s health ministry does not differentiate between militants and civilians in its casualty counts, making it difficult to gauge how many of those killed have been civilians. On Tuesday, Firass Abiad, the health minister, said that the “vast majority were unarmed people who were safely in their homes.”

“Israeli airstrikes in Lebanon are now relentlessly claiming hundreds of civilian lives,” Filippo Grandi, the U.N. High Commissioner for Refugees, wrote on X, in a statement mourning the loss of the agency’s two employees.

In addition to Ms. Darwiche, the UNHCR said one of its janitors, Ali Basma, had been killed in southern Lebanon.

Lebanon’s electricity company said Israeli strikes in the south killed one of its engineers in her home, along with her husband, children, parents and sister.

On Wednesday, employees at Electricity of Lebanon paid tribute to Farah Kajak. “She left an unforgettable mark among all her colleagues and those who worked with her,” they wrote.

Waleed Fayyad, the energy minister, said the strike on her family “reflects the extent of the brutality of the enemy, which does not respect international or humanitarian law.”

The Risala scouts, an Islamic organization that includes youth activities as well as emergency aid services, said three of its members, Ilan Basheer, Nour Touba and Hussein Moussa, were killed in their homes in southern Lebanon.

Four of Risala’s first aid responders were killed as they were working to rescue people this week, the group said.

Mr. Abiad, the minister of health, said 14 ambulances and fire engines had been targeted in Israeli strikes, killing the Risala emergency responders and wounding 16 other medics.

Lebanese media networks have also claimed losses in their ranks. On Monday, Hadi al-Sayed, a journalist with the pro-Hezbollah Mayadeen News network, was killed.

The International Federation of Journalists said Mr. al-Sayed was the fourth journalist killed by Israeli strikes in Lebanon since Oct. 7.

“Whether killed deliberately, or as collateral damage, it represents a shocking disregard for human life and the journalistic community in particular,” said Anthony Bellanger, the group’s secretary general.

Since Monday, the number has again risen: On Wednesday, the Hezbollah-affiliated Manar Television said its journalist Kamel Karaki was also killed.

“Even the sounds of regular planes freak out the kids,” said Mr. Issa, 33, holding his 3-year-old with one arm and pointing to a passenger jet overhead with the other. “That’s the reason we’re trying to get to another place.”

They had been sitting together on Monday afternoon at their farmhouse in Majidieh, a small village in green, fertile south Lebanon, when an Israeli missile struck close enough to see and hear, he said. They quickly dressed to leave, piled into the taxicab that Mr. Issa drives to make ends meet and joined the masses of cars heading toward Beirut, a journey that would normally take about two hours.

They were just a few of what Lebanon’s foreign minister has said are the half-million Lebanese displaced by Israeli airstrikes. About 400 people had come to this school-turned-shelter in the Bir Hassan neighborhood after it opened on Monday afternoon, and more were still coming through the gate, only to be turned away.

The government has designated 42 buildings as shelters, while other, private shelters have sprung up ad hoc. But after years of political and economic crisis, the country is badly equipped for this latest one and the many thousands of people fleeing to Beirut. Because the government did not provide supplies or staff, it fell to local aid groups, individual donors and volunteers affiliated with political parties to run the shelters and stock them with mattresses, bedding, food, water and medicine.

Mr. Issa’s family, like most of those fleeing, found a place to go through word of mouth and lists of shelters circulating on WhatsApp. All told, 60 members of their extended family had taken shelter in Beirut.

But Mr. Issa’s father stayed behind to take care of the house, cattle and farm, the work of 35 years.

“I’m so worried about my husband, but what can we do?” said Zeinab Awada, 60, Mr. Issa’s mother, who sat on a bench in the same clothes she was wearing when she left home, sat in traffic, slept in the car and trudged into the shelter.

Ms. Awada wiped tears from her eyes with her veil. “We couldn’t bring anything with us,” she said. “We barely managed to get dressed and get in the car and get out of there. We’ve lost everything, and now we’re homeless.”

At the shelter, there was nowhere to shower. They had been given a few thin mattresses to sleep on among the wooden desks in a classroom, and there was bread and water in the courtyard downstairs. Wires once used for hanging student artwork had been repurposed as laundry lines for the displaced.

Young men on motorbikes soon zoomed through the gate, shouting, waving and hauling black garbage bags full of snacks and other donations into the courtyard — not much, but something.

Mr. Issa said he was grateful for the help. But what comforted him more than material support, he said, was knowing that someone — what he called “the resistance,” meaning Hezbollah — was fighting for the south. It wasn’t like in the past, he said, before Hezbollah grew into a force to be reckoned with and “Israel could just march into Lebanon and no one could say anything.”

Now it was different. “Someone is defending you and your land. You’re not just pushed aside,” he said. “I left my village and my house, I left my father there, but I still feel empowered.”

He acknowledged that there was a price for such a defense. His family was homeless, their neighbor in Majidieh perhaps dead. They had not heard from him since Monday, when they said they saw four missiles strike near his house.

Others in Lebanon blamed Hezbollah for bringing such destruction to Lebanon. But Mr. Issa said it was Israel’s aggression that had caused all of this.

“People think we in the south just love death and war and blood. That’s wrong. We love life,” he said. “But at the end of the day, this is the reality forced on all of us.”

Jacob Roubai contributed reporting.

Hezbollah, the Iran-backed Lebanese militant group, said in a statement that it had launched a ballistic missile targeting the headquarters of the Mossad, Israel’s foreign intelligence service, in the suburbs of Tel Aviv. The group said the attack was in retaliation for the assassination of its leaders and the explosion of pagers and radios that incapacitated many of its members.

A spokesman for the Israeli military, Lt. Col. Nadav Shoshani, said the attack marked the first time the group had taken aim at Tel Aviv, Israel’s economic center. The missile had been headed toward civilian areas, rather than the Mossad headquarters, before it was intercepted, he told reporters in a news briefing.

“They’re trying to shoot more and farther in,” he said. “This morning, they were able to shoot farther in, the first time in history to Tel Aviv.”

Those attacks last week targeting Hezbollah leaders were followed by a barrage of Israeli airstrikes against the group in Lebanon since Monday that has killed more than 500 people, according to Lebanese authorities. The attacks have brought the two sides closer to all-out war than at any time since the start of the war in Gaza last October.

The Israeli military said its air force had struck the launcher from which the missile was fired, in the town of Nafakhiyeh in southern Lebanon.

After the Hamas-led attacks last October sparked the war in Gaza, Hezbollah began firing on Israel in solidarity with its Palestinian ally. In the year since, Israel and Hezbollah have been trading attacks, driving over 160,000 people from their homes near the border in both countries.

But Tel Aviv in central Israel has been largely sheltered from the conflict. As recently as Saturday, families were flocking to beaches and businesses were bustling in the city, 70 miles from the border with Lebanon.

Since Sunday, Hezbollah has launched more than 500 missiles, rockets and drones into Israel, most of which were intercepted. The group has appeared undeterred by the string of attacks by Israel last week.

Hezbollah, which many analysts consider the most powerful of the Iranian proxy groups and the biggest military threat to Israel, has spent years building military capacity since its war with Israel in 2006. The group was estimated to possess between 120,000 and 200,000 rockets and missiles before Israel’s strikes this week.

That set up a dizzying week of attacks in Lebanon. Israel blew up electronic devices distributed by Hezbollah, killing dozens of people and injuring thousands more. It then assassinated a group of its military leaders in an airstrike near Beirut. On Monday, a wave of Israeli airstrikes targeting parts of the country where Hezbollah holds sway killed hundreds of people.

The intensified attacks against Hezbollah reflect the opinion of some hawkish generals and others who think that the group can be forced to back down, the officials said, while others in the government believe Israel must first come to a deal on a cease-fire and hostage deal with Hamas before turning to another battleground. Prime Minister Benjamin Netanyahu has opposed a truce that would allow Hamas to survive the war.

The decision to escalate was met with strong opposition from some senior officials, according to three current and former officials who spoke to The Times. They worried that such actions, the officials said, could lead to all-out war with face-to-face fighting and questioned how they would pave the way for the return of Israelis to the north.

Hezbollah has been targeting northern Israel with rockets and drones since last year in solidarity with Hamas and its war against Israel in Gaza. Hassan Nasrallah, the Hezbollah leader, has said the group will not agree to stop firing at Israel until Israel and Hamas reach an agreement that ends the war in Gaza.

The Israeli military says that Mr. Qobeisi planned the abduction of three Israeli soldiers in 2000; their bodies were later returned to Israel in a prisoner exchange.

Israel has stepped up efforts to assassinate Hezbollah’s top leaders in recent weeks as part of a campaign to compel the Iranian-backed militant group to stop firing rockets and drones at Israel. For nearly a year, Hezbollah has been attacking Israel in solidarity with Hamas in Gaza, displacing tens of thousands of Israelis from border communities.

The campaign against the top echelon in Hezbollah comes after months of attacks that, Israeli military analysts said, have somewhat degraded Hezbollah’s military capabilities.

Over the past two months, Israel has killed at least two members of Hezbollah’s top military decision-making body, the Jihad Council, and tried to assassinate another.

In July, an Israeli airstrike in Beirut’s southern suburbs killed Fuad Shukr, one of the leaders of Hezbollah’s military operations and a confidante of the group’s leader, Hassan Nasrallah. That attack was a reprisal for a rocket attack from Lebanon that killed 12 children in the Israeli-controlled Golan Heights.

Last Friday, Israeli forces flattened a residential building in an airstrike targeting Ibrahim Aqeel, another top Hezbollah leader, alongside several other leaders of the group’s commando unit. At least 55 people were killed in the strike, including several children and other noncombatants.

And on Monday, Israel tried to assassinate a third member of the Jihad Council, Ali Karaki, with an airstrike in Beirut. Hezbollah has denied that Mr. Karaki was killed and has said he had been taken to a “safe place” in the wake of the strike.

War death tolls are estimates, and exact comparisons between conflicts are difficult. But the toll on Monday in Lebanon exceeded most daily tolls in Gaza over the past year and more than doubled the average daily death rate during the deadliest year of the Syrian civil war.

Here’s what else to know.

The number of targets struck by Israel

The Israeli military said it hit more than 1,600 targets in Lebanon on Monday, a number that has few, if any, precedents in 21st-century warfare, according to Emily Tripp, the director of Airwars, a British conflict monitor.

It is roughly 300 more than the number of targets Israel struck during the opening three days of its Gaza offensive after the Hamas-led attack on Oct. 7 — a number that itself was considered unusually high.

During the U.S.-led air campaign against the Islamic State in Iraq and Syria between 2014 and 2017, Western fighter jets struck an average of 650 targets a month across a much wider area, according to data published by the Department of Defense.

“Prior to the Gaza war, munitions deployed with this intensity and with this frequency would have been almost unheard-of,” Ms. Tripp said. “There is no comparison in terms of death toll or munitions use with previous 21st-century air campaigns of this nature, as far as we know.”

The Israeli military said Hezbollah fired 250 rockets toward Israel on Monday, most of which were intercepted by Israeli air-defense missiles or missed their targets. At least one man was reported to have been wounded by shrapnel. Since October, Hezbollah has fired more than 8,000 missiles toward Israeli positions, according to the Israeli military.

How the Lebanese death toll compares

The Lebanese health minister, Dr. Firass Abiad, said 558 people were killed on Monday in Israeli strikes — an unusually high number by the standards of contemporary war, experts said.

In Gaza last October, it took 18 days for the reported daily death toll to exceed 500. The Monday toll is about half the entire casualty count during the monthlong Israel-Hezbollah war of 2006. And it is far higher than the average daily toll during the Syrian war in 2014, the deadliest year of that decade-long conflict.

How the Lebanese government collates the death toll

Lebanon’s health ministry runs an emergency operations center that collects casualty numbers from private and state-run hospitals, collating them to create a national toll from the war, according to health officials.

These figures have historically been viewed as reliable and are cited regularly by the United Nations, which helped the ministry develop the operations center.

Hezbollah, the powerful Shiite militia backed by Iran, does not run the ministry. It is overseen by the government of Lebanon, whose members are split along sectarian and political lines.

Dr. Abiad, a former board chairman at Lebanon’s largest hospital, is generally considered apolitical and won praise and prominence for his data-driven assessments during the coronavirus pandemic. He was first proposed for the role of health minister by Saad Hariri, a Sunni former prime minister who is not allied with Hezbollah, and was formally appointed by Mr. Hariri’s successor.

The ratio of slain combatants to civilians

The Lebanese health ministry does not provide detailed breakdowns of the numbers of civilians and combatants killed. But Dr. Abiad said in a brief phone interview on Tuesday that the “overwhelming majority, if not all,” of those killed and injured on Monday were civilians.

For his statement to be true, the number of civilian men killed in Lebanon on Monday would need to overwhelmingly exceed the combined number of slain women and children. The Lebanese health ministry said that 94 women and 50 children were killed on Monday, or just over 25 percent of the total death toll, but it did not specify the number of slain male civilians.

The Israeli military has said it was targeting military operatives, weapons caches and rocket launchers, many of them hidden in civilian neighborhoods and homes.

Ms. Tripp said the number of slain women and children was “consistent with what we’ve seen in conflicts such as Iraq, but lower compared to the recent Gaza war.”

In Gaza, more than 54 percent of the roughly 34,000 people recently named as victims by the Gaza health authorities were said to be either women or boys and girls under 18. Roughly 7,000 other victims are still to be identified by the health authorities, according to the ministry’s chief statistician.

Lauren Leatherby contributed reporting.