BEIRUT: A suicide bombing that killed and wounded members of Bashar al-Assad's inner circle on Wednesday will weaken the Syrian president's support base and might accelerate high-level defections, but does not signal his imminent downfall.

"This bombing is in some ways the most successful direct attack on the regime we've had so far," analyst Gala Riani said of the attack, apparently a suicide bombing by a bodyguard which killed the defence minister as well as Assad's brother-in-law, a former intelligence chief.

Coming on the fourth straight day of fighting in the capital Damascus, the bombing, claimed by the Free Syrian Army (FSA) and also by Islamist group Liwa al-Islam, intensifies pressure on Assad and may provoke a ferocious response.

"I think the next few days are going to be crucial in signalling where the conflict goes from here," said Riani, a Middle East analyst at the Control Risks consultancy.

"At the very least, we can expect the situation to continue to deteriorate. But I think it will take more than this to take the Assad regime down."

The brazen attack at a meeting of top security officials and ministers in the heart of Damascus will send a message to the top of the Syrian government that they are vulnerable.

"It sends a stark message that individual ministers are not safe and is likely to accelerate the erosion of the regime's support base," said Anthony Skinner, head of Middle East consultancy Maplecroft.

The bombing does not alter the fact that the rebels remain hugely outgunned by Assad's forces.

"These are very significant developments, but I believe the offensive will be repelled," Skinner said. "Psychologically, though, this will likely give the FSA a significant boost and may also precipitate more defections at a senior level."