Thirty-five pro syrian government soldiers, including nine russians, have been killed in an attack according to the Syrian Observatory for Human Rights.
Earlier on Sunday the Russian Defence Ministry had put out a statement saying that four russian soldiers had been killed when several rebel groups attacked a Syrian army artillery battery.
The attack reportedly took place in the eastern Deir Ez-zor province.
The Russian military has been present in Syria supporting Bashar al-Assad at least since 2015 and about 3,000 soldiers are believed to be on the ground. According to official numbers 92 russian military personnel have died in Syria since Moscow's intervention in the conflict.