The US-backed SDF, which spearheaded the fight against the Islamic State group jihadists in Syria, instead said “six of our fighters were martyred due to a terrorist attack” with a one-way drone, targeting a “training academy in the Al-Omar oil field” around midnight.

The force condemned the attack in a statement and said the force reserved the right to respond.

The Islamic Resistance in Iraq, a loose alliance of pro-Iran fighters opposed to US support for Israel in Gaza, claimed a drone attack yesterday “against the US occupation base in the Al-Omar oil field”.

Rami Abdel Rahman, head of the UK-based Observatory, said the strike hit an SDF section inside the base, in “the first attack by pro-Iran groups against American bases after the US strikes on Syria and Iraq” late last week.

On Jan 28, a drone slammed into a base in Jordan, killing three US soldiers and wounding more than 40, an attack Washington blamed on Iran-backed forces.

The US responded on Friday with a series of unilateral strikes on Iran-linked targets in Syria and Iraq, and has said it would press on with its retaliation.

The Observatory, which relies on a network of sources inside Syria, had said at least 29 pro-Iran fighters were killed in the US strikes in Syria.

The US-led coalition was set up in 2014 to fight IS jihadists who had seized swathes of Iraq and neighbouring Syria.

Roughly 2,500 US troops are deployed in Iraq and about 900 in Syria as part of the alliance.

With US support, the SDF led the battle that dislodged IS fighters from the last scraps of their Syrian territory in 2019.

The force is the de facto army of the Kurdish semi-autonomous administration that controls swathes of Syria’s northeast.