Hezbollah supporters chant slogans during last day of Ashura, in Beirut, Lebanon, Sept. 20, 2018. Photo: Reuters / Aziz Taher / File.

A former official in the powerful Iranian-backed Lebanese group Hezbollah was found dead in his flat in a Beirut neighborhood, the state-run Lebanese news agency said on Sunday.

Security forces immediately opened an investigation and were awaiting the arrival of a forensic doctor to determine the cause of death, National News Agency said, giving only the initials of the man.

A Hezbollah official who requested anonymity confirmed the death of Ali Hatoum and told Reuters an investigation was under way but that it did not appear to be security related.

The news agency gave no other information nor what position the deceased had held in the group.

Hezbollah and the Israeli army exchanged cross-border fire last Sunday after a drone attack in a Hezbollah-controlled Beirut suburb in the fiercest fighting between the two adversaries since the 2006 Lebanon war.

Hezbollah had blamed Israel for the drone attack and its leader Hassan Nasrallah warned that it could be a precursor to assassination attacks by Israel.