Twin suicide car bombs exploded outside a military intelligence building and killed 55 people Thursday, tossing mangled bodies in the street in the deadliest attack against a regime target since the Syrian uprising began 14 months ago.
The bombings fueled 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.
The 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 2,200 pounds. "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 U.N. and Arab League envoy Kofi Annan.
The Obama administration condemned the attack and expressed concern that al-Qaida may be increasingly taking advantage of the country's prolonged instability.
Defense Secretary Leon E. Panetta told reporters that U.S. intelligence indicates "an al-Qaida presence in Syria," but said the extent of its activity was unclear.
Maj. Gen. Robert Mood, the Norwegian head of a team of observers overseeing the cease-fire, toured the site and said the Syrian people do not deserve this "terrible violence."
"It is not going to solve any problems," he said. "It is only going to create more suffering for women and children."
The government blamed the attack on armed terrorists it says are driving the uprising, which has grown into the strongest threat to the Assad family dynasty in its four decades in power.
The scope and mystery of the bombing raised fears that Syria's unrest is transforming from an Arab Spring-inspired call for change into a bloody Iraq-style insurgency.