Hashem Safieddine, the top Hezbollah official widely expected to succeed slain secretary general Hassan Nasrallah, was killed in an Israeli attack, the group said Wednesday.

Hezbollah confirmed that Safieddine was killed in an Israeli airstrike.

Safieddine had been running Hezbollah alongside its deputy secretary general Naim Qassem since Nasrallah’s assassination and was expected to be formally elected as its next secretary general, although no official announcement had yet been made.

A relative of Nasrallah, Safieddine had sat on the group’s Jihad Council - the body responsible for its military operations. He was also head of its executive council, overseeing Hezbollah’s financial and administrative affairs.

Safieddine assumed a prominent role speaking for Hezbollah during the year of hostilities with Israel that ultimately led to his death, addressing funerals and other events that Nasrallah had long been unable to attend for security reasons.

His killing further erodes the group’s top leadership as Israeli strikes pummel Lebanon’s south, eastern Bekaa Valley and southern suburbs of Beirut - all Hezbollah strongholds - and the group’s fighters seek to push back Israeli ground incursions.