BEIRUT: At least 13 civilians were killed Sunday in a missile attack by the Syrian army on a rebel-held neighbourhood in the embattled northern city of Aleppo, a monitoring group said.

"We have documented the names of nine people, while we can confirm at least another four were also killed. All were civilians," Syrian Observatory for Human Rights director Rami Abdel Rahman said.

The activists warned that the number of casualties could rise as people scrambled to sift through the rubble of a five-storey building that collapsed in the attack on Ansari district, in southwestern Aleppo.

A picture taken by an amateur photograph and distributed by the Observatory showed people gathered around a pile of rubble and the activists said two other buildings were damaged in the attack.

Large swathes of Aleppo city, once Syria's commercial hub, have been destroyed ever since the army launched an all-out assault in mid-July to stop rebels entering into the city from the neighbouring countryside.

More than 60,000 people have been killed in Syria's 22-month conflict, the UN says.