A US civilian contractor was killed in a rocket attack on an Iraqi military base near the oil-rich city of Kirkuk on Friday, US officials said.
Several US service members and Iraq personnel were also wounded, the US-led coalition fighting ISIS said in a statement.
It also said that Iraqi security forces would be leading the response and investigation into the incident.
According to Reuters, US officials said, on condition of anonymity, that the service members were lightly wounded and believed to be back on duty.
Another official said the US was looking into the possible involvement of Kataib Hezbollah, an Iranian-backed militia group.
In December, US Secretary of State Mike Pompeo blamed Iranian-backed forces for a series of attacks on bases in Iraq and warned Iran that any attacks by Tehran or proxies that harmed US or allies would be "answered with a decisive US response."
Tensions have heightened between Tehran and Washington since last year when President Donald Trump pulled the United States out of Tehran's 2015 nuclear deal with six powers and reimposed sanctions that have crippled Iran's economy.
The Iraqi military said in a statement earlier on Friday that several rockets were launched into Iraq's K1 military base, which houses US and Iraqi forces.
Security sources said security forces found a launchpad for Katyusha rockets inside an abandoned vehicle near the base.
No group has claimed responsibility for the attack, Reuters reported.
