"I've been hearing shooting and explosions for hours now and can see smoke rising from the area," a witness who spoke on condition of anonymity for security concerns told The Associated Press.

On Thursday night, armed rebels took part in a large anti-government rally in the same district, witnesses said, in a rare and bold public appearance by the fighters in the capital. Friday's fighting began when the rebels attacked a government checkpoint in the morning, according to Rami Abdul-Rahman of the Britain-based Syrian Observatory for Human Rights.

"The men are shouting 'God is great,' women are crying," said Omar, a Damascus resident who would not provide his family name for fear of reprisal by Syrian officials. The sound of machine gun fire and blasts could be heard in the background as he spoke by Skype.

A resident of the Damascus neighborhood of Qaboun said the battles began in his area after Syrian forces opened fire on an evening demonstration, killing a young man he identified as Mahmoud Said.