"Sayyed Hassan Nasrallah, Secretary General of Hezbollah, has joined his great, immortal martyr comrades whom he led for about 30 years," Hezbollah said in a statement.

The statement confirmed he was killed with other group members "following the treacherous Zionist strike on the southern suburbs" of Beirut.

In the Lebanese capital Beirut, AFP journalists heard a passerby screaming, "Oh my God", while women wept in the streets right after Hezbollah announced the news.

Gunfire could also be heard in Beirut, a gesture to mourn the fallen leader, a charismatic religious figure who is idolised by supporters.

Am AFP correspondent saw a woman wearing a black veil on the street who yelled: "Don't believe them, they're lying, Sayyed is well" -- a reference to Nasrallah.

Israeli jets pounded Beirut's south and its outskirts throughout the night into Saturday in the most intense attacks on the Hezbollah stronghold since the group and Israel last went to war in 2006.

Nasrallah had rarely been seen in public since 2006.

He was elected secretary general of Hezbollah in 1992, aged 32, after an Israeli helicopter gunship killed his predecessor Abbas al-Musawi.