Assad regime air strikes overnight put four hospitals in Aleppo province out of action, the British-based Syrian Observatory for Human Rights said on Sunday.

They included three hospitals in Aleppo city, which is divided between regime and rebel control, and one in Aleppo's western countryside, the Observatory said. It did not immediately report casualties. The strikes hit near the hospitals, it said.

Many hospitals have been hit or damaged during the five-year conflict. In April, an air strike on a hospital in rebel-held Aleppo killed dozens of people. Rebel rockets hit a hospital on the side of the city controlled by the regime a few days later.

Russian bombing raids in Aleppo had also targeted hospitals and killed many civilians.