Hezbollah leader Sayyed Hassan Nasrallah, whose death was announced on Saturday, led the Lebanese group through decades of conflict with Israel, overseeing its transformation into a military force with regional sway and becoming one of the most prominent Arab figures in generations - with Iranian backing.

Hezbollah said in a statement that Nasrallah had been killed, but it did not say how. The Israeli military said earlier it had killed Nasrallah in an airstrike on the group's central headquarters in the southern suburbs of Beirut on Friday.

Nasrallah's death deals a huge blow to the group. He will be remembered among his supporters for standing up to Israel and defying the United States. To enemies, he was head of a terrorist organisation and a proxy for Iran's Shi'ite Islamist theocracy in its tussle for influence in the Middle East.

His regional influence was on display over nearly a year of conflict ignited by the Gaza war, as Hezbollah entered the fray by firing on Israel from southern Lebanon in support of its Palestinian ally Hamas, and Yemeni and Iraqi groups followed suit, operating under the umbrella of "The Axis of Resistance".

"We are facing a great battle," Nasrallah said in an Aug. 1 speech at the funeral of Hezbollah's top military commander, Fuad Shukr, who was killed in an Israeli strike on the Hezbollah-controlled southern suburbs of Beirut.

Yet when thousands of Hezbollah members were injured and dozens killed, when their communications devices exploded in an apparent Israeli attack last week, that battle began to turn against his group.

Responding to the attacks on Hezbollah's communications network in a Sept. 19 speech, Nasrallah vowed to punish Israel.

"This is a reckoning that will come, its nature, its size, how and where? This is certainly what we will keep to ourselves and in the narrowest circle even within ourselves," he said.

He had not given a broadcast address since then.

Israel has meanwhile dramatically escalated its attacks, killing several senior Hezbollah commanders in targeted strikes and unleashing a massive bombardment in Hezbollah-controlled areas of Lebanon, which has killed hundreds of people.

Recognised even by his enemies as a skilled orator, Nasrallah's speeches were followed by friend and foe alike.

Wearing the black turban of a sayyed, or a descendent of the Prophet Mohammad, Nasrallah used his addresses to rally Hezbollah's base but also to deliver carefully calibrated threats, often wagging his finger as he does so.

He became secretary general of Hezbollah in 1992 aged just 35, the public face of a once shadowy group founded by Iran's Revolutionary Guards in 1982 to fight Israeli occupation forces.

Israel killed his predecessor, Sayyed Abbas al-Musawi, in a helicopter attack. Nasrallah led Hezbollah when its guerrillas finally drove Israeli forces from southern Lebanon in 2000, ending an 18-year occupation.