Israel says it has bombed Houthi targets in Yemen, expanding its confrontation with Iran's allies in the region two days after killing the leader of Lebanese armed group Hezbollah, Hassan Nasrallah, in an escalating conflict in Lebanon.

The air strikes on Yemen's sea port facilities and power plants on Sunday, local time, were in response to Houthi missile attacks on Israel in recent days, Israel's military said.

Houthi media said the Hodeida and Ras Issa ports had been hit, along with two power plants in Hodeida city, a stronghold for the Iranian-backed rebels.

The Houthi-run health ministry said the strikes killed four people and wounded 40 others.

Nasruddin Ammer, deputy director of its media office, said in a post on X the strikes would not stop the rebels' attacks on shipping routes and on Israel.

On Saturday, the Yemeni armed rebels launched a ballistic missile attack on Ben Gurion airport when Israeli Prime Minister Benjamin Netanyahu was arriving. 

The strikes took place as Israel attacked more targets in Lebanon, where its intensifying bombardment over two weeks has killed a string of top Hezbollah leaders and driven hundreds of thousands of people from their homes.

Israel on Sunday vowed to keep up its assault.

"It has lost its head, and we need to keep hitting Hezbollah hard," Israel's military chief of staff Herzi Halevi said.

These are the latest developments:

First attack on central Beirut

An apartment building in central Beirut was hit by an apparent Israeli air strike early on Monday morning, in the first attack within city limits through the last year of conflict between Israel and Iran's regional allies.

Witnesses told Reuters and Associated Press reporters on the ground the strike hit the top floor of a multi-storey residential building in the Kola district of Lebanon's capital.

Videos showed ambulances and a crowd gathered near the building located in a mainly Sunni district with a busy thoroughfare lined with shops.

An official with Lebanese Civil Defense, who spoke on condition of anonymity, told AP at least one person was killed in the strike and 16 people injured.

The person killed was a member of the al-Jamaa al-Islamiya, a Sunni political and militant group that is allied with Hezbollah, he said.

A security source told Reuters at least two people were killed.

There was no immediate comment from Israel's military.

In the past week, Israel has frequently targeted Beirut's southern suburbs, where Hezbollah has a strong presence, but had not hit locations near the city centre.

Seventh senior Hezbollah leader killed

Hezbollah has sustained a string of deadly blows to its command structure, including the killing of its overall leader, Nasrallah.

Deputy head of the militant group's Central Council, Nabil Kaouk, was also killed on Saturday, making him the seventh senior Hezbollah leader slain in Israeli strikes in a little over a week. They include founding members who had evaded death or detention for decades.

Kaouk was a veteran member of Hezbollah going back to the 1980s and served as Hezbollah's military commander in southern Lebanon during the 2006 war with Israel. The US announced sanctions against him in 2020.

Hezbollah had earlier confirmed that Ali Karaki, another senior commander, died in Friday's strike that killed Nasrallah. 

Israel says at least 20 other Hezbollah militants were killed, including one in charge of Nasrallah's security detail.

White House national security spokesman John Kirby said Israel's air strikes in Lebanon had "wiped out" Hezbollah's command structure, but he warned the group would work quickly to rebuild it.

"I think people are safer without him walking around," he said of Nasrallah. "But they will try to recover. We're watching to see what they do to try to fill this leadership vacuum."

Speaking on CNN's State of the Union, Mr Kirby sidestepped questions about whether the Biden administration agreed with how the Israelis were targeting Hezbollah leaders. 

Biden says 'really have to avoid' all-out war

The White House continues to call on Israel and Hezbollah to agree to a 21-day temporary ceasefire floated by the US, France and other countries as world leaders gathered for the UN General Assembly last week.

President Joe Biden said on Sunday he would speak with Mr Netanyahu, and believes that an all-out war in the Middle East must be avoided.

"It has to be," he told reporters at Dover Air Force Base in Delaware. "We really have to avoid it."

Mr Biden also said he would be speaking with the Israeli leader but did not say when: "I'll tell you what I say when I talk to him."

The United States has urged a diplomatic resolution to the conflict in Lebanon but has also authorised its military to reinforce in the region.

It has been unable to use any leverage over Israel through its recent stretch of fighting with Hezbollah. White House officials have said they received no prior intelligence ahead of the the IDF's strikes on Beirut, including the one that killed Nasrallah, this week.

But Washington was accused of complicity in the attack by Tehran, who claimed a US-supplied "bunker buster" bomb was used in the attack. US senator Mark Kelly later confirmed the bomb used to kill Nasrallah was an American-made 900-kilogram guided weapon.

Meanwhile, Mr Netanyahu on Sunday appointed a former rival, Gideon Saar, to his cabinet in a move that expands his governing coalition and helps entrench himself in office.

Under their agreement, he said Mr Saar would be given a spot in the security cabinet, the body that oversees management of the ongoing war.

Mr Saar had hoped to replace Defense Minister Yoav Gallant, another rival of Mr Netanyahu's. But that deal fell through after fighting intensified with Hezbollah.

Nearly one-fifth of Lebanon's population displaced

Elsewhere, Israeli warplanes and drones carried out deadly strikes across Lebanon on Sunday. 

Two consecutive strikes near the southern city of Sidon, about 45km south of Beirut, killed at least 32 people, including at least 14 medics, the Lebanese health ministry said. Separately, Israeli strikes in the northern province of Baalbek Hermel killed 21 people and injured at least 47.

The IDF said it also carried out another targeted strike on Beirut, but did not immediately provide details.

Lebanese media reported dozens of strikes in the central, eastern and western Bekaa and in the south, besides strikes on Beirut. The strikes have targeted buildings where civilians were living and the death toll was expected to rise.

The death toll in IDF strikes across Lebanon on Sunday stands at 105.

The IDF says its strikes have degraded Hezbollah's capabilities and the number of launches would be much higher if Hezbollah had not been hit.

In response to the dramatic escalation, Hezbollah has also significantly increased its retaliatory attacks in the past week, from several dozen to several hundred daily, the Israeli military said. 

These have mainly targeted northern Israel but most rockets and drones were intercepted by Israel's air defence systems or fell in open areas. Several injuries were reported. 

Earlier this month, Hezbollah was also targeted by a sophisticated attack on its pagers and walkie-talkies that was widely blamed on Israel. 

A wave of Israeli strikes across large parts of Lebanon have killed more than 1,030 people — including 156 women and 87 children — in less than two weeks, according to Lebanon's Health Ministry.

Hundreds of thousands of people have been driven from their homes across the country by the latest strikes. 

The government estimates around 250,000 are in shelters, with three to four times as many staying with friends or relatives, or camping out on the streets.

Iran calls for 'decisive response'

Iranian President Masoud Pezeshkian characterised the Israeli attacks on Hezbollah as a crime and said a "decisive response" was needed following the killing of numerous Hezbollah leaders.

"The Lebanese fighters should not be left alone in this battle," he said during a Sunday cabinet meeting, his office reported. He also condemned the IDF's air strikes in Yemen.

Iranian Supreme Leader Ayatollah Ali Khamenei was moved to a secure location in Iran after Nasrallah's killing, sources told Reuters.

Iran has armed and trained Hezbollah for decades and relied on it to put pressure on Israel, its chief regional rival.

Hezbollah began firing rockets, missiles and drones into northern Israel after Hamas's October 7 terror attack out of Gaza. 

Hezbollah and Hamas are allies that consider themselves part of an Iran-backed "Axis of Resistance" against Israel.

The conflict has steadily ratcheted up to the brink of all-out war, raising fears of a region-wide conflagration. Israel and Hezbollah fought a devastating month-long war in 2006 that ended in a draw.

Israel says it is determined to return some 60,000 of its citizens to communities in the north that were evacuated nearly a year ago. 

Hezbollah has said it will only halt its rocket fire if there is a ceasefire in Gaza, which has proven elusive despite months of indirect negotiations between Israel and Hamas led by the United States, Qatar and Egypt.

AP/Reuters/ABC