Government and opposition both said large numbers of people died, in one of the bloodiest days of the conflict.
Activists said artillery and helicopters were used in the worst attack, on a funeral south of Damascus.
The president's brother-in-law, the head of his crisis team and defence minister died in yesterday's bombing.
President Bashar al- Assad's own whereabouts are unknown. He has not made any public appearances since the attack.
Rebel groups said the bomb had been planted the day before the meeting at national security headquarters where it was detonated. They predicted the government's imminent fall.
The army has pledged to rid Syria of "criminal and murder gangs"
The London-based Syrian Observatory for Human Rights said on Thursday that more than 150 people had died across the country on Wednesday, in one of the worst days of a 16-month revolt.
The BBC's Jim Muir, in Beirut, says that video of one attack posted on the internet showed scenes of pandemonium after what activists said was a helicopter gunship attack on a funeral procession at Sitt Zeinab, south of the capital. They said at least 60 people were killed in this incident alone.
In Damascus, state media said, security forces launched operations in many areas which have been clashes in recent days, mainly in the south-west and north-east, killing many "terrorists".
Activists reported more tanks moving towards the capital from the west.
Following Wednesday's bombing, the government has vowed to root out ruthlessly what it describes as armed terrorists backed by outside powers.
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