Syrian activists say at least 21 people have been killed in an artillery barrage on a housing area for those displaced in rebel-held eastern Aleppo.

The Britain-based Syrian Observatory for Human Rights monitoring group said the Wednesday morning attack struck the Jub al-Quba district, where residents displaced from government advances on other areas of the city have sought protection.

It said it occurred near the site of a government airstrike that killed at least 20 the day before.

The Syrian Civil Defence search-and-rescue group put the toll at 45 dead.

It accused government forces of being behind the attack.