The government quickly held up the explosions as proof of its claims that it is battling not a popular uprising but terrorists intent on overthrowing the regime of President Bashar Assad. But its opponents cast doubt on its account, hinting that the regime itself could be behind the attack to make its case to Arab observers who arrived in the country only a day earlier.

The morning explosions left a swath of destruction, with torn bodies on the ground outside the headquarters of the General Intelligence Agency and a nearby branch of military intelligence, two agencies that have played a significant role in the bloody campaign against anti-Assad protests since March. All the windows in the military building were blown out and dozens of burned out cars lined the street.

State TV said initial investigations indicated possible involvement by the Al-Qaeda terror network. Government officials brought the advance team of Arab League observers to the scene to see the wreckage. The team arrived Thursday, the start of a mission to monitor Syria's promises to end its crackdown.

"We said it from the beginning, this is terrorism. They are killing the army and civilians," Deputy Foreign Minister Faysal Mekdad told reporters outside the intelligence headquarters.

Alongside him, the advance team's head, Sameer Seif El-Yazal, said: "We are here to see the facts on the ground ... What we are seeing today is regrettable, the important thing is for things to calm down."

Assad's regime has long contended that the violence in the country is being fueled by terrorists and foreign-backed armed gangs. In recent months, dissident soldiers have broken from the military to side with peaceful protesters and have carried out attacks on government forces. But Friday's attack was qualitatively different from any past attacks — the first suicide bombings seen during the conflict — and whoever was behind them, they add new and ominous dimensions to a conflict that has already taken the country to the brink of civil war.