Two car bombs exploded Thursday in front of intelligence headquarters in the biggest and deadliest attack reported since the uprising against President Bashar Assad's regime in March 2011.
Al-Nusra emerged in January and has claimed responsibility for attacks, including one in March on police headquarters and air force intelligence, the BBC said Saturday.
A voice on the video said Thursday's attacks were in response to attacks on civilian areas led by those loyal to Assad. Opposition activists, though, have accused Assad's regime of planning the explosions.
The compound under attack was home to two major branches of the military intelligence, one known officially as the Palestine Branch that held hundreds of prisoners and the other known as the Patrols Branch, which maintained and dispatched intelligence vehicles that patrolled the Damascus area.
The United Nations estimates at least 9,000 people have died in Syria since pro-democracy protests began in 2011, the BBC said.