Russia's military on Saturday denied that its warplanes had bombed US-backed forces in Syria's eastern province of Deir Ezzor, its spokesman told AFP.

The Syrian Democratic Forces, which is backed by Washington, said earlier Saturday that their fighters had been hit in Russian and Syrian government bombardment.

"This is not possible. Why would we bomb them?" said military spokesman Igor Konashenkov at the Hmeimim base on Syria's coast.