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

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.