An American KC-135 aerial refuelling aircraft crashed in western Iraq while a second plane involved in the incident landed safely, the US military said on Thursday.

In a statement, US Central Command said it was carrying out rescue efforts after the US KC-135 refueling aircraft went down.

“One of the aircraft went down in western Iraq, and the second landed safely. This was not due to hostile fire or friendly fire,” US Central Command (Centcom), which is responsible for American forces in the Middle East, said in a statement.

“The incident occurred in friendly airspace during Operation Epic Fury,” the statement said, using the military name of the US operation against Iran.

A US official, speaking on the condition of anonymity, said the other aircraft involved in the incident was also a KC-135 and the one that crashed had six service members on board.

The Islamic Resistance in Iraq claimed responsibility for downing the military refueling aircraft.

The group said in a statement it had shot down the KC-135 aircraft “in defence of our country’s sovereignty and airspace”.

The KC-135 is at least the fourth US military aircraft lost during the war in the Middle East, after three F-15s were shot down by friendly fire over Kuwait.

KC-135s, which have been in operation for more than 60 years, generally have a crew of three, a pilot, a copilot and a third who operates the boom used to refuel other aircraft, according to the US Air Force.

But some KC-135 missions require a navigator, and the aircraft can carry up to 37 passengers, an Air Force factsheet said.

Early in the war, which began on February 28, Kuwaiti forces mistakenly downed three American F-15E fighters, but all six crew members were able to eject, according to Centcom.

That incident occurred during combat including “attacks from Iranian aircraft, ballistic missiles, and drones,” the military command said at the time.

Additional input by Reuters