A U.S.-backed force in Syria says a Russian airstrike has wounded six of its fighters near the eastern city of Deir el-Zour.

The command of the Kurdish-led Syrian Democratic Forces said in a statement that Saturday's attack occurred on the eastern side of the Euphrates River in the industrial area that was recently liberated from the Islamic State group.

The Britain-based Syrian Observatory for Human Rights confirmed the airstrike, but said it was not clear if it was carried out by Russian or Syrian warplanes.

SDF fighters have been advancing against IS fighters on the east bank of the Euphrates while Syrian government forces and their allies are pushing on the western side against the extremists.