Syrian President Bashar al-Assad kept silent on Thursday a day after an attack on a security headquarters in Damascus killed three top regime officials, including his brother-in-law Assef Shawkat.

The embattled head of state, whose current whereabouts are still not known, rarely makes public statements and has so far not commented on the bombing or appeared in public since the attack.

However, he was cited by state media as appointing Fahd al-Freij defence minister to replace Daoud Rajha, who was among those killed when the National Security headquarters was targeted.

State media have yet to distribute images of the aftermath, unlike on previous occasions when there have been attacks in the capital. The rebel Free Syrian Army said it was behind the bombing.

Since the anti-regime revolt broke out in March 2011, Assad has made six public speeches and given several interviews to Syrian and foreign media.

His most recent speech was on 2 June, when Assad said he wanted to stamp out the revolt which he described as "terrorism".