Thousands of people have gathered in a Hezbollah stronghold south of Beirut for the funeral of a high-profile militant who the group says was killed by an Israeli airstrike near the Syrian capital.

Hezbollah said Samir Kantar, who spent 30 years in an Israeli prison for murder, was killed Saturday along with eight others in the airstrike on a residential building in Jaramana, close to Damascus.

Hezbollah pledged to avenge his killing, sparking fears of escalation in a volatile region.

Supporters of the group walked behind his coffin, which was draped in a yellow Hezbollah flag, at the funeral Monday.

"Death to Israel," the men shouted as women threw rice and rose petals at the coffin.

Hezbollah leader Sayyed Hassan Nasrallah is due to speak later Monday about his killing.