After rebels struck a blow to the heart of the Syrian regime on Wednesday, by killing at least three key members of President Bashar al-Assad's inner circle in a bombing of what amounts to the Damascus situation room, opposition figures claimed one of their biggest victories in the 16-month-long uprising.

In a series of coordinated assaults on the capital this week, billed as the “Battle for Damascus,” the rebels landed a debilitating and potentially game-changing blow to al-Assad's command structure. Syrian state television reported that the defense minister, Daoud Rajha, and the president's brother-in-law, Asef Shawkat, and Hassan Turkmani, a former minister of defense, were all killed in the attack.

An activist staying at a safe house in the old district of Damascus said rebels were spread throughout the area and controlling territory on all but the main thoroughfares, where government tanks were still parked. “We have the feeling that this is the final battle,” said the activist, who wanted only to be known as "Adam." "Pray for us, pray for us, victory is very close.”

But that outcome was far from decisive, with little indication that assaults would bring about a speedy end to the violence. By afternoon, government bombs were falling on residents in nearly all the antigovernment districts in the southern half of the city. Residents in majority-Sunni districts like Qadam were passing around grisly videos, while men in a nearby area were in the streets, on alert amid rumors that pro-regime loyalists and paramilitary forces, mostly hailing from the president's Alawi sect, had come bearing knives to carry out revenge attacks.

In an eery sign of the sectarian grievances now deeply entrenched in Syrian society, when asked who was responsible, one man from Qadam responded simply, “the Alawites.”

“We can't leave our homes,” one resident of a neutral neighborhood next to Douma told The Daily Beast. Fiercely antigovernment, the resident said he is wary of sectarian tensions simmering beneath the surface. “There were two explosions near Tishreen hospital, bodies laying over the road next to the Panorama memorial on the highway. My father saw four without heads there. My friends from Midan are moving from area to area without hope.”

Last night, he added, he saw dozens of families camped out under the Presidential Bridge, located in the center of town next to the national museum and the upscale Four Seasons hotel.

State television initially attributed the attack to a suicide bomber, but Free Syrian Army representatives disputed the account, claiming full credit for the operation. From his headquarters in Turkey, Free Syrian Army chief Riad al-Asaad told reporters that rebel forces had planted bombs inside the room where senior government officials were meeting. The attack, he added, marked “the beginning of the end of the regime.”

Corroborating his version, Omar al-Homsi, an officer with the Free Syrian Army in Damascus, told The Daily Beast that the attack was the work of the Hamza al-Shuhada battalion based in one of the city's restive suburbs. Over the past month, they coordinated with men from state security forces inside the building to plant four bombs weighing a total of 44 pounds in a fake ceiling in the room where the meeting was held. They then detonated them remotely at 11:14 a.m. In all, the operation took 10 men and a month's worth of planning, he said.

“We had to call it off three times until we could find exactly the right conditions,” said al-Homsi. “We didn't believe we'd be able to do it, but now we finally did it.” All of the men involved are safe and currently in hiding, he added.

Another group, Liwa al-Islam, or the Brigade of Islam, also claimed credit for the attack. While their Facebook page was distinctly Islamist in its imagery, it was unclear if they considered themselves part of the Free Syrian Army. They responded to a request for comment claiming credit for the attack, but did not elaborate on who they are or how they carried it out.

While details are still in dispute, the attack is indisputably a severe strike at the heart of the Syrian leadership. The national security building is located in Abou Roumaneh, a leafy, wealthy, and highly controlled area of the capital just blocks from the presidential palace.

Following the attack, security forces sealed off the area around Shami Hospital at al-Rowda Square and set up checkpoints in Abou Roumaneh, according to a member of the Revolution Leadership Council who lives there. “There is no one on the streets today, no one,” said the spokesman, who goes by the name Tariq al-Saleh. “It's the first time in my life I've seen it empty like this.”

As night fell in Damascus, the battles raged, shelling shattering restive neighborhoods from afar as rebels defended their borders. An activist in Jobr, Abu Adel, said he saw Free Syrian Army fighters shoot down two government helicopters that had been raining heavy machine-gun fire down upon his and other nearby neighborhoods, one yesterday and another today. Activists announced a series of defections of soldiers throughout the city, but said they were unable to confirm retaliatory attacks, as terrified residents tried to flee or defend themselves.

“There is a tension between people, especially today,” said the resident near Douma. “It's going to be a street war.”