A volley of approximately 14 rockets was launched at the base near the main city of Erbil’s airport late on Monday, which witnesses told local television appeared to come from the south.
Three landed inside the base while others fell on residential areas nearby, killing one person identified by a US military spokesperson as a foreign national, but not a US citizen, and injuring one US service member.
It was the most deadly attack in almost a year to hit US-led coalition forces deployed to fight Islamic State in Iraq, where tensions between the US, its Iraqi and Kurdish allies on one side and Iran-aligned militias on the other soared during Donald Trump’s presidency.
Western military and diplomatic sites have been targeted by dozens of rockets and roadside bomb attacks since 2019 which the US has blamed on pro-Iranian forces, but most of the violence has taken place in Baghdad.
The rare attack on Erbil was claimed by a little-known Shia group calling itself Awliyaa al-Dam, or Guardians of Blood – one of dozens of small groups believed to be fronts for prominent pro-Iranian factions such as Kata’ib Hezbollah and Asa’ib Ahl al-Haq.
Trump had said the death of US civilians would be a red line and provoke US escalation in Iraq, making Monday’s attack an early challenge for the Biden administration, which is seeking to revive the nuclear deal between Iran and world powers Trump scrapped in 2018.
“We are outraged by today’s rocket attack,” the secretary of state, Antony Blinken, said in a statement on Monday evening, vowing to “hold accountable those responsible”.
On Tuesday morning, Awliyaa al-Dam said it would carry out more attacks on US forces.
“The American occupation will not be safe from our strikes in any inch of the homeland, even in Kurdistan, where we promise we will carry out other qualitative operations,” a statement from the group said, according to the SITE Intelligence Group, an NGO that tracks online activity of armed organisations.