Residents reported hearing a huge explosion that rattled the Fahameh district in the centre of the capital just after sunset.
Another explosion was heard shortly after the first, but the nature of that blast was not immediately clear.
A Syrian government official said the explosion damaged nearby cars and buildings but did not say whether the police headquarters was affected.
Reports said the blast as described as a "terrorist" attack.
It was the latest in a series of bombings and suicide attacks targeting security personnel and government institutions as Syria's civil war escalates.
Damascus, in particular, has become a frequent target for car bombs and suicide blasts, but there have also been several massive bombings in the northern city of Aleppo and other cities.
On August 18, rebels carried out a sophisticated bombing of a regime security building that killed four members of president Bashar Assad's inner circle.
Last week, four bombs tore through a government-held district in Aleppo, Syria's commercial and cultural capital, killing more than 30 people and reducing buildings to rubble.