In the first significant attack in Syria or Iraq since the United States (US) launched retaliatory strikes over the weekend against Iran-backed militias that have been targeting its forces in the region, a drone attack on a base housing US troops in eastern Syria reportedly killed six allied Kurdish fighters late Sunday.

According to the Associated Press (AP), the US-backed, Kurdish-led Syrian Democratic Forces (SDF) said Monday the attack hit a training ground at al-Omar base in Syria’s eastern province of Deir el-Zour, where the forces’ commando units are trained.

The report indicated that no casualties were reported among US troops.

“An umbrella group of Iran-backed Iraqi militias, dubbed the Islamic Resistance in Iraq, released a video claiming responsibility for the attack and showing them launching a drone from an unspecified location,” the AP said.

In late January, a drone attack by the same group killed three US troops and wounded dozens more at a desert base in Jordan. The US military launched dozens of retaliatory strikes targeting Iran-backed militant groups in western Iraq and eastern Syria and also struck the Houthis in Yemen.

The AP said the SDF initially accused “Syrian regime-backed mercenaries” of carrying out Sunday’s attack but in a second statement blamed “Iran-backed militias” after investigating the attack.

The umbrella group has launched dozens of drone attacks on US military bases and troops in Iraq and Syria, and has called for the withdrawal of American soldiers from both countries. The attack comes as tensions flare across the Middle East amid the Israel-Hamas war, which was sparked by Hamas’ rampage in southern Israel on October 7.

Meanwhile, Britain-based opposition war monitor Syrian Observatory for Human Rights said at least seven SDF fighters were killed in the attack on Sunday and at least 18 others wounded, some in critical condition, the AP stated.

“The attack late Sunday came two days after the US military carried out strikes against militant targets linked to Iran in Syria and Iraq. The SDF said it has the right to respond to the attack. The US military said it struck four anti-ship missiles on Sunday that were prepared to be fired at vessels in the Red Sea from Houthi rebel-controlled areas in Yemen,” the AP reported.

In a statement early Monday, the US Central Command said the strikes were in self-defence and came after forces determined the missiles “presented an imminent threat to US Navy ships and merchant vessels in the region.”

Sunday’s strikes came a day after the US and Britain launched a second wave of strikes against the Houthis, meant to degrade the Iranian-backed group’ capabilities to attack vessels in the Red Sea. The US and Britain said they hit 36 Houthi targets, the AP said.