The blast in western Mazzeh district targeted Mr. Halaqi’s convoy, state television says.
There are reported to be a number of casualties.
United Kingdom-based activist group, the Syrian Observatory for Human Rights, said Mr. Halaqi’s bodyguard had been killed, AFP news agency reports.
BBC says it is unclear whether the blast was a suicide bombing or a planted device.
An unnamed Syrian official said the explosion was caused by a bomb placed underneath a parked car in the area..
An earlier report said it had been a suicide attack.
Syrian state television said the explosion happened at a busy intersection. Video from the scene showed burning debris and firefighters trying to put out a blaze.
A picture which activists said was of the site of the attack showed a large plume of black smoke rising into the air near a road and a high-rise building.
Activist groups said a bus and a car had been set on fire.
Mazzeh is a government-controlled quarter housing a military airport which is vital to the regime’s defences.
Syrian forces and rebels have been fighting around Damascus for months but with neither side gaining an upper hand.
The attack is the latest bombing inside government-controlled areas of the capital.