The US military has carried out an air strike targeting Iran-backed militias in Syria, in the first military action undertaken by the Biden administration. The Pentagon said the strike was ordered in response to attacks against US and coalition personnel in Iraq. The US action destroyed "multiple facilities" used by Iraqi militant groups, it said. Militia officials said one person had been killed but a war monitor reported at least 22 fatalities.

The Pentagon said its strike near the Iraqi border in eastern Syria was a "proportionate military response" that was taken "together with diplomatic measures", including consulting coalition partners.The Pentagon said the strike on Friday was launched "at President Biden's direction". It targeted facilities located at a border control point used by a number of Iran-backed militia groups, including Kataib Hezbollah and Kataib Sayyid al-Shuhada, who are allied with the Damascus government. Kataib Hezbollah and Kataib Sayyid al-Shuhada have previously carried out or supported rocket attacks targeting US assets in the country. The US has launched retaliatory strikes. But Kataib Hezbollah has denied involvement in recent attacks against US interests.

In its statement, the Pentagon said its latest operation "sends an unambiguous message". "President Biden will act to protect American and Coalition personnel. At the same time, we have acted in a deliberate manner that aims to de-escalate the overall situation in both eastern Syria and Iraq," it said.

The US did not confirm any casualties, but an Iraqi militia official told the Associated Press news agency at least one fighter was killed and a number of others wounded. The official said the strikes hit an area along the border between the Syrian city of Boukamal and the Iraqi town of Qaim.

The Syrian Observatory for Human Rights, a UK-based monitoring group, said the US attack had killed at least 22 fighters from the Popular Mobilisation Forces, an Iraqi umbrella group of mostly Shia paramilitaries that includes Kataib Hezbollah. "The strikes destroyed three lorries carrying munitions," the observatory's Rami Abdul Rahman earlier told AFP. "There were many casualties."

Several attacks targeting US personnel have been claimed by little-known groups. But some Iraqi and Western officials say these are a front for established militias, so they can carry out attacks without being held accountable. US Defence Secretary Lloyd Austin told reporters he was "confident in the target that we went after". "We know what we hit," he said. "We're confident that that target was being used by the same Shia militants that conducted the strikes" on 15 February.

What happened to congressional approval for military action?