DAMASCUS, Syria – Two suicide bombers detonated cars packed with explosives in near-simultaneous attacks on heavily guarded intelligence and security buildings in the Syrian capital Damascus Saturday, killing at least 27 people.

There have been a string of large-scale bombings against the regime in its stronghold of Damascus that suggest a dangerous, wild-card element in the year-old anti-government revolt. The regime blamed the opposition, which denied having a role or the capabilities to carry out such a sophisticated attack. And after other similar attacks, U.S. officials suggested al-Qaida militants may be joining the fray.

The early morning explosions struck the heavily fortified air force intelligence building and the criminal security department, several miles apart in Damascus, at approximately the same time, the Interior Ministry said. Much of the facade of the intelligence building appeared to have been ripped away.

State-run news agency SANA said a third blast went off near a military bus at the Palestinian refugee camp Yarmouk in Damascus, killing the two suicide bombers.

A string of previous blasts that struck the capital, also suicide bombings, have killed dozens of people since December.

The government has blamed the explosions on the “terrorists” that it claims are behind the uprising.