(CNN) A US civilian contractor was killed Friday in a rocket attack on a base near Kirkuk, Iraq, where US service members and civilian contractors were located, an Operation Inherent Resolve spokesman confirmed.

K1 military base, which houses US troops in Kirkuk province in northern Baghdad, was attacked by several katyusha rockets on Friday, according to the Iraqi military.

Several US and Iraqi military members were wounded in the attack, which happened at 7:20 p.m. Iraq time, OIR spokesman Col. Myles B. Caggins III said. A US official told CNN that "less than a handful" of Americans were wounded, and it's believed some have already returned to duty. The Iraqi military said only one Iraqi security officer was injured in the attack.

The US is now trying to determine who was responsible for the attack, officials said. The US has so far not disclosed the identity of the contractor killed, or the company they worked for. Iraqi security forces are leading the response and investigation, Caggins said.

US Secretary of Defense Mark Esper recently had asked Iraq to help prevent attacks on US personnel that both countries have attributed to groups backed by Iran.

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