The Syrian government moved quickly to stanch claims that the bombing had crippled its security apparatus. It named Fahd Jessem al Freij the new minister of defense within hours of the attacks. Freij made a statement Wednesday promising to continue the fight against “terrorist gangs,” the government’s catchall term for the opposition.

Speaking from his headquarters in southern Turkey, Free Syrian Army commander Riad al Asaad claimed responsibility for the day’s attacks. The Free Syrian Army is the moniker the majority of the rebels use, but it was unclear whether the attacks were part of a larger coordinated rebel offensive or the result of independent initiatives by local rebel commanders in Damascus.

In February and March, assaults by government troops pushed rebels out of a number of urban areas that they’d seized. But since April, the momentum appears to be in their favor as they’ve secured routes for weapons trafficking and apparently solved funding problems. Rebels have made inroads recently into areas of the cities of Deir el-Zour and Idlib they’d been kicked out of in March. A recent study by the Washington-based Institute for the Study of War found that rebel attacks on government positions surged in April and May, when a U.N.-sponsored cease-fire was supposedly in effect.

Wednesday’s bombing drew an immediate international response. The U.N. Security Council postponed a vote scheduled for Wednesday on a resolution to extend the mandate of the U.N. mission that’s in Syria to monitor the progress of the peace plan. The mandate expires Friday.

Israeli Defense Minister Ehud Barak announced that he’d summoned his top security and intelligence advisers to a meeting to discuss the situation, a move all the more startling because Israel has tried to remain publically aloof from the events unfolding in its neighbor to the north. In recent days, however, Israeli officials have expressed concern that the deteriorating situation in Syria could lead to a number of dangerous scenarios. In a parliamentary meeting Tuesday, Israel’s head of military intelligence said there was concern that Syria’s chemical weapons could fall into rogue hands, especially as the presence of foreign jihadist groups in Syria increased.

President Barack Obama spoke with Russian President Vladimir Putin but apparently failed to resolve the differences between the countries over how best to end the violence in Syria.

In comments, U.S. Defense Secretary Leon Panetta underscored the American position that no peace is possible with Assad still in office. “It is more essential than ever that the United States and the international community continue to work together, through the United Nations, through whatever possible vehicles we have, to bring additional pressure on Assad to step down and to allow for a peaceful transition of government there in Syria,” he said.

In response to the intensified fighting in the capital, the Syrian army appeared to have cut major arteries in and out of the city. Rebel fighters in al Tal and in the northern suburb of Rancous spent much of the day searching for routes into the capital in hopes of joining the fighting there, but they said the presence of Syrian army units stymied them.

Elsewhere, rebels predicted that the bombing would lead to more anti-government attacks. One rebel commander reached by phone in Idlib province in the country’s north said rebel units in the area had received no prior indication of the attack or further orders from higher Free Syrian Army command. But he thought that the intensified fighting in the capital was a signal to rebel units throughout the country.

“This is what we have been waiting for. We have our own attack here. It will be so big and we will do it so soon,” said the commander, who asked to remain anonymous out of concerns about government retaliation.

Rebel fighters repeatedly have expressed their belief that the real fight for the country will occur in Damascus. Many have said they expect a renewed offensive to coincide with the Muslim holy month of Ramadan, which begins later this week.

But it was clear also that the government hadn’t lost its ability to launch attacks. Earlier in the day, a rebel safe house in the usually peaceful Damascus suburb of Yabrud was hit by artillery or rocket fire, resulting in the deaths of five rebels. Ten rebels were wounded. It was the deadliest attack in Yabrud since the beginning of the conflict.

Reached via phone, a local rebel fighter suspected that the rebels may have been targeted by their cellphone signals. He expressed concern that the group might have a government collaborator within its ranks.

The funeral for the slain rebels drew thousands of demonstrators into the streets.

There were also reports of unexpected calm. An activist near the flash-point city of Homs said an eerie quiet had descended on the city, and that on Wednesday residents had heard no sounds of the shelling that had become part of their daily lives.

Nancy A. Youssef in Cairo, Matthew Schofield and Hannah Allam in Washington and special correspondent Sheera Frenkel in Jerusalem contributed to this article.

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