At least 10 rockets have targeted an Iraqi military base which hosts coalition troops, including UK personnel.
Iraqi security forces are investigating the incident, with took place at Al Asad airbase in the west of the country at 07:20 local time (04:20 GMT).
An American civilian contractor suffered a cardiac episode while sheltering and died shortly after.
There have been no reported injuries among US personnel.
A small number of British personnel are based at Al Asad who are understood to be all safe and well.
Colonel Wayne Marott, spokesman for Operation Inherent Resolve, the US-led coalition's mission to defeat so-called Islamic State, said "10 IDF rockets" were fired.
The Iraqi military later released a statement saying the launch pad used for the missiles had been found.
British Ambassador to Iraq Stephen Hickey has condemned the attack, saying it undermined the ongoing fight against the so-called Islamic State (IS) group.
In January 2020, 10 Iranian rockets hit Al Asad airbase, with more than 100 American personnel sustaining injuries.
British personnel were not present at the base at the time of the attack.
In February this year, the US struck an Iranian-backed, Iraqi armed group along the Iraq-Syria border, which the Pentagon said was in retaliation to a rocket attack last month that killed a civilian American contractor and wounded coalition personnel.
Around 100 UK personnel are deployed to Iraq as part of a global coalition, providing training and kit to Iraqi Security Forces and Kurdish Security Forces.
Last week, NATO defence ministers confirmed 3,500 extra alliance troops would be deploying to the country to boost its counter terrorism training mission there.
Defence Secretary Ben Wallace the UK would scale up its own commitment, which is separate to the NATO mission, in line with the alliance's expansion in Iraq.
Cover image: Library photo of ranges at Al Asad (Picture: US Department of Defense).