Beirut - A suicide car bombing at a Syrian military intelligence headquarters in Damascus province killed 53 people, a watchdog said on Friday.
The January 24 attack, reported for the first time by the Britain-based Syrian Observatory for Human Rights, was carried out by the jihadist rebel group the Al-Nusra Front, the watchdog said.
The blast targeting military intelligence in the Sahsah area of the town of Quneitra killed 53 intelligence workers including six officers and wounded 90, the Observatory said, citing medical sources.
Several bodies of prisoners being held in the building were found, but the cause of their deaths was unclear.
The Observatory relies on a network of medical sources and activists on the ground for its information.
A simultaneous explosion at a checkpoint elsewhere killed four soldiers of President Bashar al-Assad's army and sparked clashes in which a number of Al-Nusra Front fighters were killed, it said.
The United States has placed Al-Nusra, which it says is closely linked with Al-Qaeda's Iraq branch but contains mostly Syrian fighters, on its list of terrorist organisations.
The group has claimed the majority of suicide bombings in Syria's 22-month uprising against Assad, which has transformed into a full-scale civil war and killed more than 60,000 people according to UN figures. - Sapa-AFP