A car bomb explosion hit the main gate of the Syrian Interior Ministry in Damascus on Wednesday, state television said.
It said that there were casualties but did not give figures.
The ministry is in Kafar Souseh, an area of the Syrian capital that borders the central Ummayad Square and is contested between rebels and forces loyal to President Bashar al-Assad.
A resident said she heard sirens and shooting after a "huge explosion".
Rebels have made gains on the outskirts of Damascus recently but relied on hit and run attacks and bombs in the centre of the city, often on state security buildings or areas loyal to Assad, such as Jaramana, where twin bombs killed 34 people in November.
A July 18 bomb attack that killed four of Assad's closest aides, including his feared brother-in-law Assef Shawkat, was followed shortly by an inrusgent advance into the city but they were later pushed back.
At least 40,000 people have been killed in Syria's uprising, which started in March 2011 with street protests which were met with gunfire by Assad's security forces, and spiralled into the most enduring and destructive of the Arab uprisings.