Residents in the Syrian capital awoke to two loud explosions amid unconfirmed reports from activists that a major building belonging to the ruling Baath party had been by hit several rocket-propelled grenades.
There were no immediate details or confirmation of the report but the Free Syrian Army, a group of army defectors, claimed responsibility for the attack.
In a statement posted on the group's Facebook page, the FSA said the assault caused casualties and damage to the building. But eyewitnesses said the party headquarters appeared intact and reported no significant security deployment around it.
If true, the Damascus attack on the Baath Party's main building would signal a turning point in the eight-month revolution against President Bashar Assad, bringing the violence that has engulfed much of the rest of the country to the heart of the Syrian capital — so far been relatively untouched.
Assad, meanwhile, vowed to continue with a security crackdown to crush "militants" who he says are massacring Syrians on a daily basis.
"The role of the government is to fight those militants in order to restore stability and to protect civilians," he said in an interview with The Sunday Times.
"We have to prevent militants from doing what they are doing now, killing civilians doing massacres, in different places in Syria."
He also repeated earlier warnings that any foreign military intervention in Syria would "shake the entire Middle East."
Syria's uprising against Assad, although largely peaceful, has grown more violent and militarized in recent weeks, as frustrated protesters see the limits of peaceful action. Army dissidents who sided with the protests have also grown bolder, fighting back against regime forces and even attacking military bases.
The Free Syrian Army group of dissident soldiers this week staged their boldest operation yet, striking a military intelligence building in a Damascus suburb.
If confirmed, the attack would mark the first significant assault on a government building in what has so far been a relatively quiet central Damascus.
The Local Coordination Committees activist network and several residents reported several explosions in the district of Mazraa in the heart of the Syrian capital.
The LCC said in a statement that the building had been hit at daybreak Sunday by several rocket-propelled grenades and that two fire brigades headed toward the area amid a heavy security presence. The group said it had no further details.
Residents in the Syrian capital said they heard two loud explosions but could not confirm whether the building had been hit.
"I woke up to the sound of two loud thuds," said a resident of the area who asked that he remain anonymous for fear of reprisals. "We have no idea what they were."
Damascus-based journalist Thabet Salem, who lives about a half mile (1 kilometer) away from the Baath party building and heard the explosions, said if the reports are confirmed, it would signal a new phase in the Syrian uprising.
"It would be an escalation that gives a new dimension to the whole situation," he said.
The UN says more than 3,500 people in Syria have been killed in the crackdown since the start of the uprising in mid-March. Assad, in the interview, said over 800 Syrian officers and security forces were killed.
The interview came a day after the passing of an Arab League deadline for Syria to comply with an Arab peace plan and accept observers. Syrian TV said the country's foreign minister later Sunday will announce Damascus' position on the Arab initiative.
Assad lashed out at the 22-member organization and said the initiative was aimed at giving the international community an excuse to meddle in his country.
"It's been done to show that there's a problem between the Arabs, thus providing Western countries with a pretext to conduct a military intervention against Syria," he said.
The consequence of any such intervention, he warned, would be "an earthquake that would shake the entire Middle East."
Assad said he feels "pain and sorrow" for the bloodshed but added the solution was to eliminate the militants he blames for much of the violence. The Assad regime maintains the militants are playing out a foreign agenda to isolate and weaken Syria.
"The conflict will continue and the pressure to subjugate Syria will also continue," Assad said. "However I assure you that Syria will not bow down and that it will continue to resist the pressure being imposed on it," he added.
Assad, who took over power from his late father, Hafez, in 2000, said there would be parliamentary elections in February or March, after which there would be a new government and new constituion.
"That constitution will set the basis of how to elect a president ... the ballot box should decide who should be president."