Lebanese Shiite militant group Hezbollah on Saturday blamed Sunni extremists for killing its top military commander in Syria and vowed to keep fighting to defend President Bashar al-Assad's regime.
The Islamist State (IS) jihadist group, meanwhile, briefly overran a government-controlled hospital in the eastern city of Deir Ezzor, triggering a battle with pro-regime forces in which 59 fighters were killed, a monitor said.
Hezbollah has deployed thousands of fighters in Syria where Mustafa Badreddine had led its intervention in support of Assad's forces, which are also backed by Russia and Iran.
Badreddine, who was on a US terror sanctions blacklist and wanted by Israel, was killed in an explosion on Thursday night near Damascus international airport.
Hezbollah announced his death on Friday but without immediately apportioning blame, breaking with its usual pattern of accusing arch-foe Israel of responsibility.
On Saturday, it said a probe had concluded that Sunni Islamist radicals known as "takfiris", who consider Shiites to be heretics, had killed Badreddine.
"An investigation has shown that the blast that targeted one of our positions near the Damascus international airport that led to the martyrdom of the brother commander Mustafa Badreddine was caused by artillery bombardment carried out by takfiri groups present in that region," a Hezbollah statement said.
It did not name any specific group, and there has been no claim of responsibility.
Hezbollah has been battling opponents of Assad's regime including Sunni extremists from IS and Al-Nusra Front, Al-Qaeda's Syria affiliate.
Hezbollah fighters carry a portrait of Mustafa Badreddine during his funeral in the Ghobeiry neighbourhood of Beirut on May 13, 2016 -- AFP / Anwar Amro
