US forces stationed in Syria conducted a strike on Tuesday after they were fired on in Deir Ezzor province, the Pentagon said.
Press secretary Maj Gen Pat Ryder said shells from mortars and rocket launchers landed near a US base called MSS Euphrates.
“We're still assessing who is operating these weapons. But we do know that there are Iranian-backed militia groups in the area that have conducted attacks on MSS Euphrates in the past,” Maj Gen Ryder told reporters.
The US has about 900 troops in Syria, mainly in the north-east, where they have been based since 2015 to help local troops fight ISIS.
A small number of US troops are at the base in a gasfield in Deir Ezzor and have occasionally conducted strikes in the region, including against Iran-backed forces.
“There are also Syrian military forces that operate in the area. To be clear, the self-defence actions successfully eliminated imminent threats to US personnel and were not linked to any broader activities in north-west Syria by other groups,” Maj Gen Ryder noted, referring to recent rebel advances in Aleppo.
In a separate incident on November 29, US forces engaged a “hostile target” with an A-10 attack plane after men were seen preparing a rocket, he added.
“The self-defence actions likewise eliminated threats to our personnel at MSS Euphrates,” Maj Gen Ryder said, stressing that the strike was in no way related to operations in and around Aleppo or north-west Syria.
