"Coalition forces conducted a strike against a Daesh cell near Busayrah", a town in Deir Ezzor province, said coalition spokesman James Rawlinson, using an Arabic acronym for IS.

"This operation eliminated five terrorists who played a key role in facilitating attacks across the region against security forces and innocent civilians," he told AFP.

The five jihadists were all Syrian, according to the Syrian Observatory for Human Rights war monitor.

It was the first aerial attack by coalition warplanes since IS was driven out of its last holdout in Syria four months ago, the Britain-based group added.

A US-backed, Kurdish-led force announced it had expelled the extremists from their last patch of territory in eastern Syria, the town of Baghouz, on March 23.

That came after a months-long campaign backed by coalition air strikes.

The Syrian Democratic Forces' victory spelt the end of the jihadist proto-state declared in 2014 after IS seized large parts of Syria and neighbouring Iraq.

But despite losing their territory, IS fighters continue to launch regular attacks across war-torn Syria.

They have claimed operations in SDF-held areas, including targeted killings and setting fire to vital wheat crops.

In Syria's vast desert, they have repeatedly hit regime forces with deadly attacks and ambushes.

They also maintain a presence in the northwestern region of Idlib, which is dominated by an Al-Qaeda-linked jihadist group.

The US-led coalition has said it is backing the SDF in northeastern Syria against thousands of remaining IS loyalists.

"The coalition will continue to enable partner forces in their pursuit of enduring defeat of Daesh," Rawlinson said.

He said that "with coalition support, the SDF have been conducting back clearance operations, with over 200 Daesh members detained and 3,000 pounds (1,360 kilos)" of unexploded ordnance recovered.

The war in Syria has killed more than 370,000 people and displaced millions since it started in 2011 with a brutal crackdown on anti-government protests.