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.

“All our windows and doors are blown out,” said Majed Seibiyah, 29, who lives in the area of one of the blasts. “I was sleeping when I heard a sound like an earthquake. I didn’t grasp what was happening until I heard screaming in the street.”

The first explosion around 7 a.m. targeted the air force intelligence building in the residential district of al-Qassaa, a predominantly Christian area. It caused destruction in a 100-meter radius, shattering windows, blowing doors off their hinges and throwing chairs and other furniture off balconies.

State TV aired gruesome images of the scene, with mangled and charred corpses, bloodstained streets and twisted steel.

It carried interviews with the wounded in hospital.

“Is this the assistance promised by Qatar and Saudi Arabia?” asked one of the injured.

The two Gulf powerhouses have been fiercely critical of the Syrian government’s crackdown on dissent and have been discussing military aid to the rebels. The U.N. says well over 8,000 have died since the uprising began a year ago, inspired by Arab Spring revolts across the Middle East and North Africa.

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