BEIRUT — A suicide car bomb attack on a military convoy in northeastern Syria on Monday killed five members of a Kurdish-led force accompanying US troops in an anti-militant coalition, a monitor said.

The attack, claimed by Daesh (the so-called IS) group, came less than a week after another deadly attack on US forces in Syria and a month after Washington announced a US troop pullout from the war-torn country.

The Syrian Observatory for Human Rights monitoring group said five fighters from the Kurdish-dominated Syrian Democratic Forces (SDF) were killed in the blast on a road in Hasakeh province.

"A suicide attacker driving a bomb-laden car targeted a convoy of American forces accompanied by the SDF on the Hasakeh-Shadadi road," the observatory said.

Shadadi lies to the south of Hasakeh, capital of the eponymous province, which has been relatively spared by the war that erupted in Syria nearly eight years ago.

The coalition confirmed the attack by a vehicle-borne improvised explosive device, but said there were no US casualties.

"A combined US and Syrian partner force convoy was involved in an apparent VBIED attack today in Syria," coalition spokesman Sean Ryan said on Twitter.

"There were no US casualties.

'Grey smoke'

The head of the Britain-based observatory, Rami Abdel Rahman, said the attacker had ploughed into an SDF vehicle.

Footage on Kurdish media showed a plume of grey smoke rising up from a narrow road flanked by dry land.

A witness told AFP the blast took place by a checkpoint held by Kurdish forces a dozen kilometres (around 8 miles) outside Shadadi as the US convoy drove past.

The witness said he heard planes fly overhead, before the area was completely cordoned off by Kurdish fighters.

The Kurdish Asayesh security forces said no one had died in the attack, which hit ten meters from a checkpoint outside Shadadi.

"A bomb-laden car driven by a terrorist tried to target a coalition convoy as it passed by, lightly wounding a female member of the Asayesh," the statement said, reporting no other casualties.

Daesh propaganda channel Amaq claimed the attack on a joint US-Kurdish convoy.

The attack came less than a week after another attack on the US-led force and its local partners in the strategic city of Manbij.

Four Americans — two members of the military, a Pentagon civilian and a contractor — were killed in a blast that targeted a restaurant in the city center on Jan. 16.

It was also claimed by Daesh.

The Manbij attack cost Washington its worst combat losses since it deployed in the war-torn country to combat militants, who established a self-proclaimed "caliphate" across swathes of Iraq and Syria in 2014.

Ten civilians and five SDF fighters were also killed in the Manbij attack.

The US Department of Defense had previously reported only two American personnel killed in combat in Syria, in separate incidents.

This month's attacks targeting the US-led coalition and its allies follow US President Donald Trump's shock December announcement that he had ordered a complete troop pullout from Syria, as IS had been "largely defeated".

Trump and other senior US officials have since sent mixed messages about the pace and scope of the withdrawal.

Turkey has repeatedly urged Washington to make way for its own military plans in northern Syria, where the beleaguered Kurds are increasingly turning to the regime and its Russian sponsor for support.

The SDF is fighting to expel Daesh fighters from the remaining shreds of the extremist group's "caliphate" in a small pocket of land in eastern Syria near the Iraqi border.

Syria's complex war has killed more than 360,000 people and displaced millions since it started with the brutal repression of anti-government protests in 2011. — AFP