"The number of martyrs in the Israeli enemy strike on Beirut's southern suburbs rose to 12 people with 66 wounded, including nine in critical condition," the ministry said, adding rescuers were still looking through the rubble.

Requesting anonymity to discuss sensitive matters, the source close to Hezbollah said the strike on the militant group's stronghold in south Beirut had killed the head of its elite Radwan unit, Ibrahim Aqil.

"The Israeli air strike killed Radwan Force commander Ibrahim Aqil, its armed force's second-in-command after Fuad Shukr," the source close to Hezbollah said.

Hezbollah has not officially confirmed his death, but it said after the strike that it had hit an Israeli intelligence base it claimed was responsible for "assassinations".

The air strike is the third to hit the southern suburbs of Beirut since the start of the Israeli war on Gaza, with the focus of the violence shifting dramatically this week from Gaza to Lebanon.

Hezbollah's Al-Manar television broadcast live footage from the scene of the attack that showed ambulances rushing to the area and transporting injured people on stretchers.

Lebanon's state-run National News Agency reported "an enemy raid targeting an apartment in a residential building in the Al-Jamous area of the southern suburb" of Beirut.

Earlier this year, strikes blamed on Israel killed top Hezbollah commander Fuad Shukr, and a leader of its allied Palestinian group Hamas, Saleh al-Aruri.

Footage posted on social media and verified by AFP showed smoke rising over southern Beirut on Friday.

*This story was edited by Ahram Online.