Russian air strikes have killed more than 9,000 people in war-torn Syria in the past year, a Syrian opposition monitoring group which tracks the country's civil war has said.

The Britain-based Syrian Observatory for Human Rights said on Friday the victims include both civilians and fighters, among them rebel groups as well as militants from the Islamic State group and an al Qaida-linked faction.

On September 30 last year, Russia began an air campaign backing forces of the Syrian President Bashar Assad and turning the balance of power in his favour.

Opposition activists have blamed Russia for the recent air campaign against rebel-held neighbourhoods of Aleppo city which has killed more than 200 civilians in the past two weeks and demolished buildings.

The Observatory says the air strikes have killed 9,364 people over the past year.