Islamic State group jihadists on Thursday killed at least 18 regime fighters in an attack in central Syria, a war monitor said.

Pro-government fighters backed by Russian air strikes were battling off the jihadists on the outskirts of the desert town of Al-Sukhna in Homs province, the Syrian Observatory for Human Rights said.

The air raids and clashes killed 11 IS fighters, the Britain-based monitor said.

"The Russian aviation intervened to stop the jihadists from advancing and retaking the town," Observatory chief Rami Abdel Rahman said.