Syrian television said the car had been rigged with 440lb of explosives and went off at Sidi Kadad near a security checkpoint on the airport road.

All the victims were reported to have been civilian passers by. Reporters were barred from approaching the scene of the attack, which was sealed off by security forces.

The explosion, which also injured at least 14 people, was the first blast in Syria since February, when another car bomb killed Imad Moughniyah, the head of Lebanon's Hizbollah militia group.

Some outside observers have speculated that that attack was the motivation behind the assassination of a top Syrian commander involved in the country's nuclear programme in August.

It is not yet clear whether the bomb was directed at the security installation, the airport or at Shia pilgrims flocking to the Sit Zeinab shrine.

Zeinab was the Prophet Mohammed's granddaughter through his favourite daughter Fatima and son-in-law Ali - one of the four Sunni "righteously guided" Caliphs, and the first of the Shia Imams.

She is the subject of great devotion from Shia pilgrims from Iran, Iraq and Lebanon.