Russian airstrikes have killed 21 IS fighters in the Syrian desert.
The Syrian Observatory for Human Rights said more than 130 airstrikes had been carried out in the past 24 hours in large parts of the Iraqi border province of Aleppo.
Rami Abdul Rahman, head of the Syrian Observatory for Human Rights, said it was difficult for Russia to conduct operations because IS fighters did not have a specific location.
Because they are scattered and do not stay in one place.
