Firefighters have put out a fire that broke out before daybreak Friday at a fuel storage in the international airport of the Syrian capital Damascus, the state- run SANA news agency said.

Quoting airport officials, SANA said aviation movement is " totally normal" now, and an investigation is underway.

However, pro-opposition activists said the fire broke out after the rebels Free Syrian Army fired mortar shells at the airport from the nearby sprawling suburb of Ghouta, east of Damascus.

The attack came to ease the pressure the rebels is feeling in the Ghouta suburb after the Syrian army beefed up its presence there, the activists said, adding that Syria's air force have carried out several airstrikes in nearby areas to secure the road for ambulances and fire engines.

Another report from the pan-Arab al-Mayadeen TV said an airplane also caught fire at one of the airports' runways early Friday.

The Western-backed rebels have been waging attacks against several airports and airbases across the country, in what observers said is an attempt to weaken the ability of the Syrian air force so as to set the stage for possible foreign military intervention.