Israel said it killed Hezbollah's chief of staff in an air strike on Lebanon's capital on Sunday, hitting an apartment building in an operation the militant group said crossed a red line.

Lebanon's health ministry said the attack in Beirut, which came after Prime Minister Benjamin Netanyahu vowed Israel would "do everything necessary" to prevent the pro-Iran movement from regrouping, killed five people and wounded 28 more.

The ministry did not give the identities of those killed in the strike, which took place in the Haret Hreik area in Beirut's southern suburbs, a densely populated area where Hezbollah holds sway.

In a statement shortly after the strike, the Israeli military said it had "eliminated the terrorist Haytham Ali Tabatabai, Hezbollah's chief of general staff".

It was the fifth Israeli strike on Beirut's southern suburbs since a ceasefire agreed in November 2024 after a year of conflict, and comes a week before Pope Leo XIV is scheduled to visit Lebanon.

The Israeli military insisted in its statement that it "remains committed" to the ceasefire.

Hezbollah said a senior commander was targeted in the strike, without confirming if they were killed.

"The targeting was clearly aimed at a key... figure in the resistance, and the results are unknown," Hezbollah official Mahmud Qomati told reporters in front of the strike location,saying the attack "crosses a new red line".

He was speaking before Israel said it had succeeded.

An AFP correspondent at the scene said the strike hit the third and fourth floors of a nine-storey building, where ambulance and fire crews scrambled to find survivors and Lebanese soldiers deployed to secure the site.

Debris littered the road below, with several burned-out cars seen in the street.

The AFP journalist saw rescue workers evacuating a body wrapped in a white bag and at least three wounded women from the site.

"I was on the balcony. There was a flash, then I hit the railing and all the glass broke," a man who was in a building opposite the targeted apartment told AFP, refusing to give his name.

Lebanon's official National News Agency said three missiles were fired at the building.