The bombings fuelled fears of a rising Islamic militant element among the forces seeking to oust President Bashar Assad and dealt a further blow to international efforts to end the bloodshed.
The first car bomb went off on a key six-lane highway during the morning rush hour, knocking down a security wall outside the government building and drawing people to the scene, witnesses said.
A much larger blast soon followed, shaking the neighborhood, setting dozens of cars ablaze and sending up a gray mushroom cloud visible around the capital.
Syrian state TV video showed dozens of bodies, some charred or dismembered, strewn in the rubble or still inside damaged cars. An Associated Press reporter at the scene saw medics in rubber gloves picking through the site for human remains amid the two craters that were blasted into the asphalt.
T he Interior Ministry, which oversees the police and security services, said 55 people were killed and more than 370 were wounded. Officials said suicide bombers detonated explosives weighing more than 1,000 kilograms.
"The house shook like it was an earthquake," Maha Hijazi said, standing outside her home nearby. World powers seeking to halt Syria's unrest condemned the attack and urged all sides to adhere to a cease-fire brokered by UN and Arab League envoy Kofi Annan.
"In order to prevent another escalation of violence, we continue to call on the Syrian regime to fully and immediately implement the Annan plan," State Department spokeswoman Victoria Nuland said in Washington.