Syrian opposition activists are reporting more than a dozen airstrikes on rebel-held parts of the northern city of Aleppo.

Thursday's airstrikes came a day after an air raid hit east Aleppo's biggest market, killing at least 15 people and leveling buildings.

The Britain-based Syrian Observatory for Human Rights reported more than 20 airstrikes on eastern Aleppo, adding that clashes were taking place between government forces and insurgents on the city's northern edge.

The Halab Today TV channel reported "intense" airstrikes on rebel-held parts of Syria's largest city, adding that cluster bombs were being dropped.

The Observatory said Wednesday that at least 358 civilians have been killed in eastern Aleppo since a U.S. and Russian-brokered truce collapsed on Sept. 19. The U.N. says over 100 children have been killed since then.