Opposition forces and Syrian army units were locked in fierce clashes around elite Republican Guard posts in the suburbs of Damascus on Tuesday, a monitoring group said.

"Violent clashes are taking place around positions of the Republican Guard in Qadsaya and Al-Hama," eight kilometres from central Damascus, Syrian Observatory for Human Rights head Rami Abdel Rahman said.

"This is the first time that the regime uses artillery in fighting so close to the capital," he said. "This development is important because it's the heaviest fighting in the area and close to the heart of the capital."

"These suburbs are home to barracks of troops which are very important for the regime like the Republican Guard. This is also where families of [army] officers live," he said.

-- AFP