The United States carried out air strikes against Iran-backed militias near the Iraq-Syria border in response to drone attacks on its forces in Iraq.
Pentagon spokesman John Kirby said the strikes targeted “operational and weapons storage facilities” at three locations.
President Biden had been clear he would act to protect US personnel, he added.
The targeted facilities were at two locations in Syria and one inside Iraq, and were used by several Iran-backed groups, including Kataib Hezbollah and Kataib Sayyid al-Shuhada, the Pentagon said.
US media reported that the strikes were carried out by US Air Force F-15s and F-16s using satellite-guided munitions.
“The United States took necessary, appropriate, and deliberate action designed to limit the risk of escalation – but also to send a clear and unambiguous deterrent message,” Mr Kirby said.
A powerful Iraqi militia alliance, the Popular Mobilisation Forces (PMF), said four members of one faction were killed and threatened to retaliate.
About 2,500 US troops are in Iraq as part of a global coalition supporting local security forces in their fight against the jihadist group Islamic State (IS).
There have been at least five drone attacks against facilities they use since April, US officials say. Rockets are also frequently fired at them.
IRAQ IRAN REACTION
Iraq’s military said the strikes represented a clear breach of Iraqi sovereignty.
Military spokesman Gen Yehia Rasool tweeted: “We condemn the US air attack that targeted a site last night on the Iraqi-Syrian border, which represents a blatant and unacceptable violation of Iraqi sovereignty and Iraqi national security.”
He reiterated Iraq’s “refusal to be an arena for settling scores” and appealed for calm.
Iran also condemned the strikes. Foreign Ministry spokesman Saeed Khatibzadeh told reporters in Tehran that the US should “refrain from taking emotional steps, creating crises and tensions, and multiplying problems for people in the region”.
Syrian state media reported that a child was killed in a strike near Syria’s border with Iraq, and accused the US of seeking to undermine efforts to improve stability in the area.
The Syrian Observatory for Human Rights, a UK-based monitoring group, reported that at least seven militia fighters were killed in the strikes.