A Department of Defence statement said the US contractor had been killed and the others wounded “after a one-way unmanned aerial vehicle struck a maintenance facility on a Coalition base near Hasakah in northeast Syria.”
Another US contractor was also injured in the UAV attack, the Pentagon said, adding that the US intelligence community “assess the UAV to be of Iranian origin.”
Defence Secretary Lloyd Austin said that at the direction of President Joe Biden, he had authorized “precision airstrikes tonight in eastern Syria against facilities used by groups affiliated with Iran’s Islamic Revolutionary Guards Corps.”
“The airstrikes were conducted in response to today’s attack as well as a series of recent attacks against Coalition forces in Syria by groups affiliated with the IRGC,” he added.
Hundreds of US troops are in Syria as part of a coalition fighting against remnants of the Islamic State (IS) group and have frequently been targeted in attacks by militia groups.
The US troops support the Syrian Democratic Forces (SDF), the Kurds’ de facto army in the area, which led the battle that dislodged IS from the last scraps of their Syrian territory in 2019.
Two of the service members injured on Thursday were treated onsite, while the three other troops and one US contractor were medically evacuated to Iraq, the Pentagon said.
“As President Biden has made clear, we will take all necessary measures to defend our people and will always respond at a time and place of our choosing,” Austin said.
When the strikes were announced, Biden had already travelled to Canada, where he is set to meet with Prime Minister Justin Trudeau and address Parliament.
Last August, Biden ordered similar retaliatory strikes in the oil-rich Syrian province of Deir Ezzor after several drones targeted a coalition outpost, without causing any casualties.
That attack came the same day that Iranian state media announced a Revolutionary Guard general had been killed days earlier while “on a mission in Syria as a military adviser.”
Iran says it has deployed its forces in Syria at the invitation of Damascus and only as advisers.
The IRGC is the ideological arm of the Iranian military and is blacklisted as a terrorist group by the United States.