Three people have been killed at an army base in Iraq where British personnel are stationed.
A US official confirmed on Wednesday that two of those killed at the Camp Taji base were American troops, but declined to comment on the nationality of the third.
A Ministry of Defence spokesman said they were aware of an incident involving UK service personnel at the base.
Some 10 people were injured in the attack, according to the US official, who spoke on condition of anonymity.
US military spokesman Colonel Myles Caggins said that more than 15 small rockets had hit the base.
Camp Taji, located just north of Baghdad, has been used as a training base for a number of years. There are as many as 6,000 U.S. troops in Iraq, training and advising Iraqi forces and conducting counterterror missions.
Officials did not say what group they believe launched the rocket attack, but Kataib Hezbollah or another Iranian-backed Shia militia group is likely.
Kataib Hezbollah was responsible for a late December rocket attack on a military base in Kirkuk that killed a U.S. contractor, prompting American military strikes in response.
That in turn led to protests at the U.S. embassy in Baghdad. They were followed January 3 by a U.S. airstrike that killed Iran’s most powerful military officer, Gen. Qassem Soleimani, and Abu Mahdi al-Muhandis, a leader of the Iran-backed militias in Iraq, of which Kataib Hezbollah is a member.
Kataib Hezbollah been designated a “foreign terrorist organisation” by the State Department since 2009.