Two children were among at least 13 people killed in new air strikes on a rebel-held district of Syria's main northern city of Aleppo on Tuesday, a watchdog said.

It was the third straight day of air raids on the eastern Shaar neighbourhood of the city, Syria's commercial hub before a rebel offensive in July last year made it a key battleground in the conflict which erupted in March 2011, the Syrian Observatory for Human Right said.