"IS has since Monday carried out several attacks on Syrian army and allied positions and checkpoints in the Badia (desert) of Raqa, killing 13 members of regime forces," the Syrian Observatory for Human Rights said.

Rami Abdel Rahman, head of the Britain-based monitoring group, told AFP the regime has retaliated with waves of air raids, killing 15 jihadists either in the strikes or fighting on the ground.

Since its defeat in Syria in March 2019, IS has carried out regular deadly attacks on the army and Kurdish forces.

In August, the jihadists claimed an attack near the city of Deir Ezzor that killed a general and two other soldiers of the Russian army forces allied to the Damascus government.