The Lebanese Shia movement Hezbollah on Saturday said that its top commander in southern Beirut, Mustafa Badreddine, was killed near Damascus International Airport in shelling carried out by opposition forces fighting the Syrian regime.
Hezbollah announced Badreddine’s death on Friday and organised a military funeral for him.
"Investigations have showed that the explosion, which targeted one of our bases near Damascus International Airport, and which led to the martyrdom of Commander Mustafa Badreddine, was the result of artillery bombardment carried out by takfiri groups in the area," Hezbollah said in a statement.
However, a monitoring group denied opposition groups had shelled the area.
The killing of Mustafa Badreddine is being dubbed the biggest blow to the Iranian-backed organisation since its military chief was killed in 2008.
The 55-year-old was one of the highest ranking officials in the group and is believed to be responsible for Hezbollah's military operations in Syria.
Hezbollah is fighting alongside the Syrian regime.
An internal investigation is underway to figure out whether he was killed by an air strike, missile attack or artillery bombardment.
Badreddine was indicted for his involvement in the 1983 bombings of the US and French embassies in Kuwait that killed five people.
He was detained in Kuwait and imprisoned for several years until he fled jail in 1990, after forces sent by then Iraqi leader Saddam Hussein invaded the country.
He was also being tried in absentia for the assassination of former Lebanese Prime Minister Rafik Hariri in an explosion.