The brazen attack that killed several senior leaders of the Syrian government Wednesday represents a profound psychological blow that could loosen President Bashar al-Assad's grip on power, several experts said.

The blast followed a sharp increase in fighting in Damascus in the past few days and marked the most significant attack on al-Assad's inner circle in 16 months of fighting that government opponents say has killed more than 16,000 people. It killed the country's defense minister, emboldened anti-government rebels and immediately raised questions about the stability of al-Assad's regime.

Due to a translation error, an earlier version of this article erroneously reported that the interior minister had been killed as a result of Wednesday's explosion at a national security building in Damascus. He was injured in the blast, but he is alive and in stable condition, according to Syrian state television. CNN regrets the error.

"How long it can withstand the pressure it is under is an open question, but it seems likely that it will not be able to withstand them indefinitely," said Jeffrey White, a defense fellow for the Washington Institute for Near East Policy think tank and a former member of the U.S. Defense Intelligence Agency. "Things are tilting more and more against the regime."

He said he believes that trend is becoming irreversible.

Stephen Starr, a freelance journalist who spent the past five years in Syria and is author of the book "Revolt in Syria," said the attack signals a new stage in the conflict.

"I think actually we are entering the final stage of the revolution; the regime is probably going to fall," he said.

The attack could prompt more Syrian troops to defect, analysts said. It could also stretch the military thin if al-Assad moves reinforcements to Damascus from other parts of Syria that have been engulfed in conflict.

U.S. Defense Secretary Leon Panetta said Wednesday that the violence in Syria "is rapidly spinning out of control," but several experts warned against overstating the bombing's effect.

Dan Plesch, director of the Centre for International Studies and Diplomacy at the School of Oriental and African Studies in London, warned against seeing the attack as a turning point.

"We shouldn't exaggerate it," he told CNN. "Clearly, it's very serious for the regime, and all the international attention that comes from what in any other environment one would call a terrorist action against the Syrian defense minister and the Defense Ministry."

But, he said, "I think it's too early to talk about the imminent fall of the regime because the army as a whole still seems to be a coherent and large and very heavily armed force."

Jordan's King Abdullah II, one of the first Arab leaders to call for al-Assad to step down, told CNN that he didn't think the attack means the regime is about to crumble.

"This was a tremendous blow to the regime, but again, Damascus has shown its resilience, so I think maybe we need to keep this in perspective," the king said told CNN's Wolf Blitzer. "Although this is a blow, I'm sure the regime will continue to show fortitude, at least in the near future."

Analysts long have said that there could be a turning point in Syria if the unrest that has raged in major provincial cities such as Homs, Hama, Daraa, and Deir Ezzor were to spread to the larger cities of Damascus and Aleppo.

In recent months, attackers have staged high-profile bombings in those cities and battles have raged in Rif Damashq, the province that includes the Damascus suburbs.

White said the latest attack and the fighting in the heart of the capital expose the vulnerability of al-Assad's regime.

"It's in the regime's backyard," he said. "The people who run the place can see it or hear it."

White said the armed opposition has grown in power and includes growing numbers of defectors and civilians called the Free Syrian Army as well as jihadist groups.

A focus on Damascus could weaken Syria's security push in the other cities besieged by al-Assad's soldiers and militia allies, White said.

"If they can't bring the thing under control in Damascus, then they will probably bring in reinforcements outside of Damascus," he said.

He noted that the military "has withstood the stresses of a year of combat against an increasingly capable opponent, the steady expansion of its task, and a running wound in the form of defections and casualties."

White said the Russian and Iranian governments, longtime friends and allies to al-Assad, are constantly assessing the situation. Russia will try to avoid being "caught on the wrong side" and Iran "will never come out against the regime," but it may back away from al-Assad, he said.

Rime Allaf, an associate fellow at the Chatham House think tank, supported theories that the attack was the work of an insider: "Someone who has the full trust of the upper echelons of the regime and over a period of time gathered all these explosives until this bomb was detonated," she said.

The attack could signal a rift in the regime, with people in top posts who disagree with al-Assad "taking matters into their own hands."