A powerful car bomb has struck a petrol station in the Syrian capital of Damascus, killing 11 people and injuring dozens more, activists reported.

The death toll is likely to increase as the explosion took place when a large group of people were queuing up to buy fuel in the war-torn country, according to the Britain-based Syrian Observatory for Human Rights.

Television images showed burnt bodies of the victims while the rescuers searched frantically for the injured under the rubble. The explosion took place reportedly after a booby-trapped car was detonated.

The blast took place in the northern part of Damascus, where there is a large population of Alawites, an offshoot of Shiite community to which the Syrian President Bashar al-Assad belongs.

State-owned media agency reported the attack and blamed it on "terrorists", the term Assad's regime uses to describe rebels.

The pro-Assad al-Ikhbariya television said nearly 30 people had been killed in the attack.

"The station is usually packed even when it has no fuel. There are lots of people who sleep there overnight, waiting for early morning fuel consignments," an unnamed opposition activist told Reuters.

This is the second time such an attack has taken place on a petrol station and follows the aerial attack earlier this week which incinerated dozens.

Other neighbourhoods of Damascus also witnessed skirmishes between Assad's troops and the armed opposition groups.

The rebels during their attempt to capture the Taftanaz air base in the Idlib province were forced to withdraw by Assad's forces.

Although the Syrian rebels have advanced in several parts of the country, Assad continues to maintain a firm grip over the capital.

The lightly-armed Syrian rebels have been struggling to match the Syrian troops for the past 21 months. More than 60,000 people are estimated to have been killed during this insurgency period against Assad.

The UN recently said the death toll has been "truly shocking" and added that the figures appeared to have reached than it was previously thought.