AMMAN/BEIRUT A Syrian rebel group claimed responsibility for the Damascus bombing that killed four of President Bashar al-Assad's top aides, releasing video purporting to show the building minutes after the blast and radio messages from panicky security forces.
The video, circulated by the "Military Leadership of Damascus City and Province" in the name of the "Hawks Special Operations Battalion" showed drifting smoke near the National Security Bureau building in the Damascus district of Abu-Rummaneh which was struck, though no sign of outward damage.
Rebels using the name of other groups have already claimed to have carried out the July 18 attack. But the video, downloaded onto the Internet on Saturday, was the first to show the apparent aftermath of the brazen blow against Assad's inner circle.
Regional security experts who saw the video said it was apparent the camera had been fixed on the street where the National Security Bureau is located, near the now abandoned U.S. ambassador's residence, well before the explosion.
"Whoever took the video knew something was about to happen there, although they did not film the exact explosion, which appears to have killed its targets at close quarters from inside the building," one of the sources said.
The eight-minute video showed a steady and clear shot of the building, unlike much of the footage distributed by Syria's opposition, suggesting that the camera could have been set up in advance, although it did not show the moment of the blast.
A voice-over on the video, speaking in the name of the "Military Leadership of Damascus", said the attack was carried out using explosive devices placed inside the building.
It said the explosion targeted a meeting of Assad's "crisis cell" to "root out the heads of tyranny and oppression and corruption" in Syria.
It added that the bombing was a response to massacres and violations across Syria by Assad's forces as they have sought to crush the 16-month uprising against his rule.
Syrian authorities said the bomb attack killed Assad's brother-in-law Assef Shawkat, seen as the strategic brain behind the crackdown on the uprising, the defense minister, a veteran army general, and Hisham Bekhtyar, head of the National Security Bureau.
"Bashar. Your end will come from those closest to you. Either you leave or stray dogs will eat your flesh," the voice in the video said.
It included recordings of apparently intercepted radio messages between anxious security forces calling for ambulances to be sent to the location in the aftermath of the attack.
"Clear the road to the National Security roundabout quickly! Operations, send a patrol car quickly. Clear the road!" shouted one officer.
"Jisr al-Abyad, send me three motorbikes to Jisr al-Abyad!" said another, referring to an intersection on the road between the blast and the hospital where the casualties were taken.
An opposition source in contact with the Hawks battalion said it was composed of ex-army officers who are "the most professional among the rebels groups". The source added that last month they attacked the Marj al-Sultan military airport near Damascus and destroyed several helicopters .
"They work quietly, and effectively," the source said.
Syrian forces bombarded parts of Damascus with helicopter gunships on Sunday, witnesses said, clawing back territory from the rebels a week after the fighters launched what they called a final battle for the capital.
(Editing by Mark Heinrich)