A video posted online in the name of a militant group is admitting responsibility for twin suicide bombings in the Syrian capital in which 55 people died.
A group calling itself the Al-Nusra Front said the bombing was in response to attacks on residential areas by the regime of President Bashar Assad.
"We fulfilled our promise to respond with strikes with explosions," a distorted voice said in the video.
The video's authenticity could not be independently verified. The Al-Nusra Front has claimed past bombings in Syria through posts on militant websites. Little is known about the group.
The bombing on Thursday in Damascus raised fears that al Qaida-linked extremists are joining the anti-Assad fight.