Two suicide car bombs detonated near a government intelligence building in Damascus, Thursday, killing at least 55 people and wounding nearly 400 others.
Eyewitnesses described the explosions as highly coordinated with the first blast detonating at the height of morning rush hour and a second, larger blast, following close behind to maximize casualties.
A statement by the interior minister described "two booby-trapped cars loaded with more than 1000 kg of explosives."
Syrian media outlets and city officials loyal to President Bashar Assad blamed foreign-backed, anti-Assad terrorist groups for the attack.
Russian Foreign Minister Segei Lavrov, a close ally to Assad, also cited foreign involvement.
"Some of our foreign partners are doing practical things so that the situation in Syria explodes in a literal and figurative sense," he said.
But opposition leaders argue the explosions were orchestrated by Assad to create fear and smear their efforts.
Thursday was the deadliest terror attack in the capital since the uprising began in March 2011.
In the past 16 months nearly 9,000 people have been killed. Seventy United Nations observers are currently in the country to preserve a shaky cease-fire.