"At least 14 members of the regime forces were killed" and several others wounded "in a bloody IS attack on a military bus" in the desert near the ancient city of Palmyra, the Syrian Observatory for Human Rights said.

Syria's defence ministry confirmed the attack in a statement issued later, but gave a lower death toll.

It said eight soldiers had been killed in a "terrorist attack" on an army bus in the desert, south of Palmyra.

Last week, IS killed nine Syrian government soldiers and militiamen in an attack on military posts in the eastern desert, according to the Britain-based Observatory.

IS proclaimed a "caliphate" in June 2014 across swathes of Syria and Iraq and launched 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.

More than half a million people have been killed in the civil war which erupted in Syria in 2011 after Damascus brutally suppressed anti-government protests.