BEIRUT — A lethal bomb attack in Damascus struck at the heart of President Bashar Assad’s inner circle Wednesday, killing at least three of his most senior aides, including his minister of defense and brother-in-law, in the most audacious challenge to the government’s grip on power since the Syria uprising began 17 months ago.
The multiple assassinations immediately called into question the continued ability of the state to function effectively, penetrating deep into the core of a regime that relies almost exclusively on an insular group of loyalists to organize and implement its military response to a now armed uprising.
In Washington, Defense Secretary Leon E. Panetta said Syria ‘‘is rapidly spinning out of control,’’ and warned the government to safeguard its large stockpile of chemical weapons.
“It’s obvious what is happening in Syria is a real escalation,’’ he said at a joint news conference with the British defense minister, Philip Hammond.
By hitting the very military structure that has directed the government’s response to the uprising, the Syrian opposition struck a serious blow not only to Assad’s brain trust, but also to the psychological advantage his superior military strength has provided in preserving loyalty of his forces and frightening the public to stay home. With the opposition energized and the government demoralized, analysts wondered if the day’s events would now inspire other military units and trusted lieutenants to switch sides.
The idea that a poorly organized, lightly armed opposition force could reach deep into the inner sanctum raised fresh questions about the viability of a once unassailable police state. The Assad family has for decades relied on overlapping security forces and secret police to preserve its lock on power. At best, for Assad, the system failed. At worst, for Assad, its agents were complicit in staging the explosion.
The assassinations were the first of such high-ranking members of the elite since the revolt began and could represent a turning point in the conflict, analysts said.
The nature and target of the attack strengthened the opposition’s claims that its forces have been marshaling strength to strike at the close-knit centers of state power. State television reported that the explosion was caused by a suicide bomber, while a commander in the Free Syrian Army, the main armed opposition group, said the attack was from planted explosive devices detonated remotely.
Assad made no public statement about the attack, and his whereabouts were not immediately clear. The attack, after three days of fighting in the capital, seemed to heighten tensions between government soldiers and the opposition, with fierce clashes reported in several Damascus neighborhoods. There was also a rash of reported defections from the government side.
According to state television, the dead included the defense minister, Dawoud Rajha; Assef Shawkat, the president’s brother-in-law who was the deputy chief of staff of the Syrian military; and Hassan Turkmani, a former minister of defense and military adviser to Vice President Farouk Sharaa.
But the television report rejected claims by Arab satellite channels that the minister of the interior, Mohammed Shaar, also was killed, saying he was injured and in stable condition.
Rajha was appointed minister of defense in August. A Christian, he was one of the prominent minority figures used by the Assad government to put a face of pluralism on the military and security services dominated by the president’s Alawite sect.
The British-based Syrian Observatory for Human Rights, an anti-Assad activist organization, said all the members of the crisis group set up by Assad to try to put down the revolt were either dead or injured. State television said that besides the three dead and the injured interior minister, the only other injured was Hisham Ikhtiar, head of the general security bureau.
The government moved rapidly to project an image of control, naming General Fahd Jassem al-Freij, the military chief of staff and a man once assigned to subdue restive Idlib province in the north, as the new minister of defense. In a statement read by Freij on state television, he said the military would not be deterred from ‘‘cutting off every hand that harms the security of the homeland and citizens.’’
The attack came as diplomatic maneuvers to seek a cease-fire remained deadlocked by differences between Syria’s international adversaries and sponsors, principally Russia, ahead of a UN Security Council vote on a Western-sponsored resolution that would threaten Assad’s government with economic sanctions if it does not implement a peace plan negotiated by the special envoy Kofi Annan more than three months ago.
The resolution, which Russia has threatened to veto, would also extend the mission of 300 unarmed UN monitors, whose work has been suspended because of the violence.