Hezbollah’s most senior commander in the Syrian war, Mustafa Amine Badreddine, has been killed
A 55-year-old was killed in a large explosion near Damascus airport.
An Israeli airstrike was initially blamed by Hezbollah for the attack in which he died, but that claim was later withdrawn.
The Lebanon-based terrorist group announced his death in a statement on the website of its al-Manar network.
Hezbollah said: "He took part in most of the operations of the Islamic resistance since 1982."
In a second statement, it said: "The investigation will work on determining the nature of the explosion and its causes and whether it was a result of an air, missile or artillery attack.
"We will announce further results of the investigations soon."
Israel has not commented on his death.