The US military has attacked Iranian-backed militant groups in Iraq, hours after US personnel were injured in a drone strike on a US airbase there.
The US defence chief said three sites used by Kataib Hezbollah and other groups were hit in response to attacks on US forces in Iraq and Syria.
The US strikes were condemned by Iraq as a "clear hostile act".
The US has repeatedly targeted sites linked to militant groups in Iraq and Syria in recent years.
Iraq said one person was killed and 18 others, including civilians, were injured in the US strikes.
Secretary of Defence Lloyd Austin said the attack, which he called "necessary and proportionate", was authorised by President Joe Biden.
The earlier drone strike, on a US base in Irbil in Iraq's Kurdistan region, injured three US military personnel, one critically, US National Security Council spokesperson Adrienne Watson said.
A militia collective called Islamic Resistance in Iraq, linked to Kataib Hezbollah, said it was behind the the attack.
The Irbil airbase has previously been hit by rocket attacks carried out by Iranian-linked militia. Kataib Hezbollah, which is financed and armed by Iran, has been one of the most prominent groups involved in attacks on US targets in Iraq. It forms part of the Hashd al Shaabi (Popular Mobilisation), an umbrella group of militia which has been integrated into the Iraqi armed forces.
Iraq is an ally of both the US and Iran, which are major foes of one another. The US has about 2,500 soldiers in Iraq at the invitation of the Iraqi government to prevent a resurgence there of the Islamic State (IS) group. There are about 900 US military personnel in north-east Syria, also to curb IS, though the Syrian government considers their presence illegal.
