Syrian rebels downed a helicopter gunship on Friday in eastern Damascus province, home to some of the rebel Free Syrian Army's fiercest and best organised battalions, a monitoring group said.

"It emerged that the rebels downed a helicopter gunship over the town of Saqba in the Eastern Ghuta area," said the Syrian Observatory for Human Rights.

Initially, the Britain-based Observatory had reported that the aircraft was a fighter jet.

"Allahu akbar! (God is greatest). The helicopter is falling!" said an unidentified youth whose voice was heard on amateur video posted on YouTube by activists on Friday.

"He hit it! He hit it!" another young man can be heard yelling as the helicopter gunship is seen tumbling out of the sky, leaving a trail of flames and smoke.

"The heroes of Eastern Ghuta have downed a helicopter," the man adds.