A rebel fighter with the Jaish al-Islam (Army of Islam) places their flag in the snow during a training session in Eastern al-Ghouta, a rebel-held region outside the capital Damascus on January 11, 2015.

An ambush by Syrian rebels on pro-regime forces near Damascus this week killed 76 fighters, a monitor said Saturday, in one of the deadliest attacks of its kind since the conflict began.

Militants from the powerful Jaish al-Islam (Army of Islam) rebel group opened fire last Sunday on around 240 government forces that were preparing to storm the opposition stronghold of Eastern Ghouta, the Syrian Observatory for Human Rights said.

The Observatory said at the time of the attack, which it described as “the largest ambush of regime forces in the war”, that 35 people had died.

Director Rami Abdel Rahman on Saturday gave a new toll, documenting 45 pro-regime fighters killed by gunfire and another 31 killed when landmines were detonated during the clashes.

At least 100 remain unaccounted for, Abdel Rahman added.

Families of those killed or missing — many of whom hail from the coastal province of Latakia — are demanding to receive the bodies of their loved ones, he told AFP.

Jaish al-Islam is the strongest opposition faction in Eastern Ghouta, a large suburb of Damascus that is regularly bombarded by government forces.

The regime has struggled to take back territory there despite air support from its ally, Russia.

More than 260,000 people have been killed and millions have been forced to flee since Syria’s war erupted in 2011.

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