"Five pro-regime fighters were killed in clashes with IS militants," the head of the Syrian Observatory for Human Rights, Rami Abdel Rahman, told AFP.

IS captured large swathes of Syria and Iraq in 2014, proclaiming its "caliphate" and launching a reign of terror.

It was defeated territorially in Syria in 2019 but its remnants continue to carry out deadly hit-and-run attacks and ambushes, particularly from desert hideouts, targeting both pro-government forces and Kurdish-led fighters.

On January 9, an IS attack killed at least 14 soldiers aboard a military bus in the Syrian desert near Palmyra, the Observatory reported.

The conflict in Syria, sparked in 2011 by the Damascus government's iron-fisted repression of pro-democracy demonstrations, has left more than half a million dead.