A second Islamist militant group has claimed responsibility for Wednesday's assault on a Syrian army headquarters in the heart of Damascus, in a statement posted to the Internet.
Al-Nusra Front said on a jihadist website on Thursday that it was behind the attack on the heavily guarded headquarters in the capital.
Al-Nusra Front was unheard of before the Syrian revolt erupted in March 2011. It has claimed the majority of suicide attacks over the course of the conflict, including a twin suicide bombing in Damascus in May that killed 55 people.
It said that a suicide bomber detonated an explosives-laden vehicle outside the headquarters.
Amid the panic, four Al-Nusra members disguised in military uniforms were able to trick the security guards into letting them into the building, after which a three-hour gun battle ensued, according to the group.
Al-Nusra said all five men were killed in the attack, whose description was strikingly similar to one given the day before by a separate Islamist group.
On Wednesday, an Islamist rebel group calling itself Tajamo Ansar al-Islam (Gathering of Partisans of Islam) claimed responsibility for the attack.
It said a suicide bomber blew up his vehicle at the entrance of the headquarters, while bombs planted in the third floor of the building were made to go off at the same time.
Five of its fighters, including a suicide bomber, were killed in the attack, a statement added.
State media said the attack on the heavily guarded site killed four guards and sparked a gun battle between troops and rebels.
For its part, the Britain-based Syrian Observatory for Human Rights, as well as a rebel officer, said the attack was an inside job.