DAMASCUS - A loud explosion occurred Sunday evening at al-Mazzeh neighborhood, west of the Syrian capital Damascus, witnesses and local media said.

According to witnesses, the blast lit up the sky over al-Mazzeh before the big blast rattled building windows along a distance of three kilometers.

The state media reported the blast but did not specify the exact target.

However, the Britain-based Syrian Observatory for Human Rights said the blast was caused by a car bomb that ripped through a checkpoint near the military airport of al-Mazzeh.

The airport is close to the troublesome suburbs of Daraya and Muadamieh where intense battles have been raging on between the Syrian troops and the Western-backed rebels.

The rebels charge that the airport is responsible for the bulk of airstrikes against Daraya and Muadamieh.

But the activists' report could not be checked independently with the absence of official statement.