An Israeli air raid in Beirut killed Hassan Nasrallah, Hezbollah’s long-time leader, the Lebanese militant group confirmed on Saturday.

Mr Nasrallah is the most powerful target killed by Israel in weeks of intensified fighting and a significant escalation in the war in the Middle East, this time between Israel and Hezbollah.

The Israeli military said it carried out a precise air strike on Friday while Hezbollah leaders were meeting at their headquarters in Dahiyeh, south of Beirut.

The Lebanese health ministry said six people were killed and 91 injured in the strikes, which levelled six apartment buildings.

Ali Karki, the commander of Hezbollah’s southern front, and other commanders were also killed, the Israeli military said.

A statement from Hezbollah said Mr Nasrallah – who led the group for more than three decades – “has joined his fellow martyrs”.

The group vowed to “continue the holy war against the enemy and in support of Palestine”.

Iran announced on Saturday that a prominent general in its paramilitary Revolutionary Guard sanctioned by the US died in the same air strike.

Abbas Nilforushan, 58, who the US identified as the deputy commander for operations in the Guard, was killed on Friday, Iran’s state-run IRNA news agency reported.

Palestinian militant group Hamas sent condolences to its ally Hezbollah and said “assassinations will only increase the resistance in Lebanon and Palestine in determination and resolve”.

Immediately after the confirmation from Hezbollah, people started firing in the air in Beirut and across Lebanon to mourn Mr Nasrallah’s death.

Iran’s supreme leader announced five days of public mourning after Mr Nasrallah’s death. Ayatollah Ali Khamenei called Mr Nasrallah “the flag-bearer of resistance” in the region.

Smoke rises as a building collapses in Beirut’s southern suburbs
Smoke rises as a building collapses in Beirut’s southern suburbs (Hussein Malla/AP)

Hundreds of protesters, meanwhile, took to the streets of Tehran, waving Hezbollah flags and chanting “Death to Israel” and “Death to Netanyahu the murderer”.

Thomas Juneau, a professor at the University of Ottawa’s Graduate School of Public and International Affairs, said Iran will be under significant pressure to respond to Mr Nasrallah’s killing without escalating violence in the region.

“Iran understands that its military options are limited, given the conventional military superiority of Israel and the US,” Mr Juneau told The Associated Press.

Israel’s Chief of Staff Lieutenant General Herzi Halevi said on Saturday that the elimination of Mr Nasrallah was “not the end of our toolbox”, indicating that more strikes were planned.

Defence minister Yoav Gallant called it “the most important targeted strike since the founding of the State of Israel”.

Israel has vowed to step up pressure on Hezbollah until it halts its attacks that have displaced tens of thousands of Israelis from communities near the Lebanese border.

Smoke rises from destroyed buildings in Beirut’s southern suburbs on Saturday morning
Smoke rises from destroyed buildings in Beirut’s southern suburbs on Saturday morning (Hussein Malla/AP)

The recent fighting has also displaced more than 200,000 Lebanese in the past week, according to the UN.

Air raid sirens sounded across central Israel on Saturday afternoon, including at the Tel Aviv international airport, shortly after Prime Minister Benjamin Netanyahu returned from a trip to the US.

The Israeli military said it intercepted a missile launched from Yemen. It was not immediately known if the missile strike was aimed at Mr Netanyahu’s flight.

The Israeli military updated guidelines for Israeli citizens, cancelling gatherings of more than 1,000 people due to the threat.

Approximately 60,000 Israelis have been evacuated from their homes along the Lebanese border for almost a year.

This month, Israel’s government said halting Hezbollah’s attacks in the country’s north to allow residents to return to their homes is an official goal.

Hezbollah started firing rockets on Israel in support of Gaza on October 8, a day after Hamas militants launched an unprecedented attack on Israel, killing some 1,200 people and abducting another 250.

Israel Prime Minister Benjamin Netanyahu  holds up maps
Israel Prime Minister Benjamin Netanyahu addresses the 79th session of the United Nations General Assembly on Friday (Richard Drew/AP)

Since then, the two sides have been engaged in escalating cross-border strikes.

Earlier this month, thousands of explosives hidden in pagers and walkie-talkies used by Hezbollah detonated, killing dozens of people and maiming thousands, including many civilians. Israel is widely believed to be behind the attack.

On Saturday morning, the Israeli military carried out more than 140 air strikes in southern Beirut and eastern Lebanon’s Bekaa Valley, including targeting a storage facility for anti-ship missiles in Beirut suburb of Dahiyeh.

Israel said the missiles were stored beneath civilian apartment buildings.

Hezbollah launched dozens of projectiles across northern and central Israel and deep into the Israel-occupied West Bank, damaging some buildings in the northern town of Safed.

In Beirut’s southern suburbs, smoke rose and the streets were empty after the area was pummelled overnight by heavy Israeli air strikes.

A total of 1,030 people — including 156 women and 87 children — have been killed in Israeli strikes in Lebanon in less than two weeks, the country’s health minister said on Saturday.