Dozens of Syrian rebels were killed in an ambush by government troops near the capital Damascus.

Opposition activists said at least 62 rebel fighters were killed at dawn near the Damascus suburb of Adra.

"At least 62 rebels fell as martyrs, most of them youths," Britain-based Syrian Observatory for Human Rights said.

State news agency Sana confirmed the ambush and claimed the rebels were from the al-Qaida and allies from the al-Nusra Front.

The "terrorist" - as the regime led by president Bashar al-Assad labels all rebel groups - included men of other nationalities apart from Syrian fighters, Sana added. A number of machine-guns and rocket-propelled grenades were confiscated.

Adra, in the Eastern Ghouta region, has been under siege for months as government troops have launched an offensive to regain grounds around Damascus.

Earlier this week, Syrian rebels rallied after a spate of government victories, gaining control of a strategic airbase near the border with Turkey.

The Mannagh military airport, north of Aleppo, was reportedly seized by Islamic State of Iraq, al-Fateh brigade and other al-Qaida linked rebel battalions.

The base was the largest to fall into rebel hands since opposition forces captured the Taftanaz base in the northern province of Idlib in January.

Last week, Assad's forces captured a key district in the central city of Homs.

More than 100,000 people have been killed since Syria's conflict started in March 2011.

READ: Syria: al-Qaida-Linked Rebels Capture Key Airbase outside Aleppo