BEIRUT — Chaos reigned in Damascus on Wednesday as rebel forces attacked the heart of the Syrian regime in their most brazen maneuver in the 16-month-old revolt.
Top-level officials, including the Syrian defense minister and the brother-in-law of President Bashar Assad, were killed in an explosion at the National Security building, a headquarters for one of Syria’s intelligence branches that is near Mr. Assad’s private residence and less than 500 yards from the U.S. Embassy. The embassy has been closed since Washington withdrew its ambassador several months ago.
The White House said the bombing showed that Mr. Assad is "losing control" of Syria.
Islamist groups have claimed responsibility for the blast, but the rebel Free Syrian Army also announced that it carried out the attack in coordination with informants inside the government.
In Washington, President Obama phoned Russian President Vladimir Putin, one of Syria’s strongest allies, while Defense Secretary Leon E. Panetta said Syria is "spinning out of control."
The explosion at the highest levels of Mr. Assad’s government sparked conflicting accounts over whether the blast was caused by a suicide bomber, while conspiracy theories swept the Syrian capital that the attack was a cover-up for a military coup. The explosion followed four straight days of clashes between rebels and government troops this week in Damascus.
"People are leaving these affected areas. These areas that are under shelling. They are leaving their homes for safer places," said Lena al-Shami of the Revolution Leadership Council of Damascus. "Life is not that normal in Damascus anymore."
The explosion at the National Security headquarters during a Cabinet meeting killed Defense Minister Dawoud Rajiha, 65, and Deputy Defense Minister Gen. Assef Shawkat, Mr. Assad’s 62-year-old brother-in-law and head of military intelligence. Gen. Shawkat was one of the most feared figures in the regime.
Hassan Turkmani, 77, a former defense minister, died as a result of his wounds in a hospital. Interior Minister Mohammed Shaar and Maj. Gen. Hisham Ikhtiar, who heads the National Security Department, were wounded but reported in stable condition in a hospital.
Mr. Rajha was the most senior Christian government official in Syria, and his death is expected to resonate with Syria’s Christians, who make up about 10 percent of the population of 22 million and have mostly stood by the regime. Christians say they are particularly vulnerable and fear that Syria will become another Iraq, with Christians caught in the crossfire between rival Muslim groups.
Suicide bomber or rebel attack
Syrian officials blamed a suicide bomber for the attack, but the rebel Free Syrian Army said its forces had planted a bomb in the room where the Cabinet meeting was held. A rebel spokesman called the attack "the beginning of the end of the regime."
"The Free Syrian Army proved that they can reach anywhere in Syria, even though they don’t have fighters everywhere and have limited arms," said an activist in Damascus who asked not to be named for fear of retaliation.
"This will cause great confusion in the leadership of the regime and will encourage more operations for the [rebel army] and will quicken getting rid of Assad."
Speculation about the killings has been rife. Some analysts say that someone from within the regime must have been responsible for helping rebels target the meeting.
"It doesn’t give an indication of how strong the opposition is, but it raises many questions of how they got in there and how they got the information, whether they had a collaborator inside," said Nadim Shehadi, an associate fellow at the London think tank Chatham House.
"The regime will be thinking, 'Who betrayed us?' If they feel the regime has lost its main strength, they may feel encouraged to defect," he said.
A cloak-and-dagger rumor circulating in Damascus suggested that the attack could have been orchestrated as part of a military coup or that it was staged by the regime itself.
Fear in Damascus
As the violence escalates, activists claim that whole parts of Damascus have fallen out of state control. In al-Tadamon, a poor district about five miles south of the city center, activists said the conditions were like a siege.
"In Tadamon, there is no water, no electricity," said Jacob Hussein, a 30-year-old activist with the Local Coordination Committee. "We use batteries. We use sometimes generators. We find many ways actually to get water, to get food supplies. We have just the Free Syrian Army defending Tadamon and not letting anybody in."
He said tens of thousands have fled the district and were massing inside the nearby Yamouk camp for Palestinian refugees.
"Now the majority of al-Tadamon neighborhood is displaced," Mr. Hussein said. "Our Palestinian brothers are hosting them now."
After the deaths of some of those closest to the regime, some residents said they were scared of what might happen next.
"We are afraid of any act of retaliation from the regime’s part," said Ms. al-Shami of the Revolution Leadership Council of Damascus.
Others say the fighting moving to the capital marks the beginning of the end.
"The regime right from the beginning was keen to show Damascus as a safe zone with normal life because this is the capital and the headquarters of all the secret service and the regime media," said an activist who asked not be named.
"Damascus has a different nature than other parts of Syria because of this, and killing those criminals in their own places is a clear message that there’s no safe place for them wherever they run and hide. That’s why the nature of resistance in Damascus is different from other places."
What is clear, analysts say, is that all of those involved will be considering what they can do next.
"Huge complex calculations are happening in the minds of everybody involved in Syria," Mr. Shehadi said. "The impact is much more important than military action. People are expecting more defections, but they are not easy in the regime because everybody is watching everybody else."
In Moscow, a Kremlin spokesman said Mr. Obama, in his phone call to Mr. Putin, failed to persuade the Russian leader to endorse tougher sanctions against Mr. Assad. "Differences in approaches remain," he said.
In Washington, the State Department raised concerns that the security apparatus surrounding Mr. Assad is beginning to falter.
"We think the regime is losing control in Syria," said State Department spokesman Patrick Ventrell, who added that U.S. officials are "watching the situation very closely" amid concerns that a chaotic power vacuum could open if Mr. Assad is assassinated.
Unease over the development was palpable at the Pentagon, where Mr. Panetta told reporters that Syria’s security situation is "spinning out of control." He was joined by British Defense Minister Philip Hammond, who added that "there is a sense that the situation is deteriorating and is becoming more and more unpredictable."
Both men stressed the need for the international community to unite and to put collective pressure on the Syrian government to persuade Mr. Assad to step down. U.S. officials hope such a development could open the window for a peaceful political solution to the mounting violence between the Syrian military and opposition forces.
The Treasury Department on Wednesday announced measures to freeze the assets of 29 senior Syrian government officials, but past attempts to impose broader sanctions have been weighed down by diplomatic resistance from Russia, which maintains a naval base in Syria.
U.S. officials lobbied the U.N. Security Council on Wednesday to enact a resolution allowing for wider sanctions against the Assad government. Russia has threatened to veto such a resolution.
• Mr. Resneck reported from Hasankeyf, Turkey, while Louise Osborne in Berlin and Guy Taylor in Washington contributed to this article, which is based in part on wire service reports.