Three United States service members have been killed and dozens are feared wounded after an unmanned aerial drone attack US forces stationed in northeast Jordan near the Syrian border, President Joe Biden and US officials say.

Biden blamed Iran-backed groups for the attack, the first deadly strike against US forces since the Israel-Hamas war erupted in October and sent shock waves throughout the Middle East.

“While we are still gathering the facts of this attack, we know it was carried out by radical Iran-backed militant groups operating in Syria and Iraq,” Biden said in a statement on Sunday.

“Have no doubt – we will hold all those responsible to account at a time and in a manner of our choosing,” he said.

Biden later asked for a moment of silence for the three killed service members during a campaign event in South Carolina.

“We shall respond,” he said.

US Defence Secretary Lloyd Austin echoed that threat.

He and other senior officials briefed Biden earlier in the day on the attack.

At least 34 personnel were injured in the attack, but that number is expected to change as more people seek care, US Central Command said in a statement.

Eight personnel were evacuated from Jordan for higher-level care and were in stable condition.

Two US officials said the drone struck near the barracks early in the morning.

The Islamic Resistance in Iraq, an umbrella organisation of hardline Iran-backed militant groups, claimed attacks on three bases, including one on the Jordan-Syria border.

The attack is a major escalation of the already tense situation in the Middle East, where war broke out in Gaza after Palestinian Islamist group Hamas attacked Israel on October 7, killing 1200.

Israel’s subsequent assault on Gaza has killed more than 26,000 Palestinians, according to the local health ministry.

Since then, US forces have come under attack more than 150 times by Iran-backed groups in Iraq and Syria, causing at least 70 casualties before Sunday’s attack, most of them traumatic brain injuries.

US warships have also been fired at by Iran-backed Houthi forces in Yemen, who are regularly attacking commercial ships passing through Red Sea waters off Yemen’s coast.

While the US has thus far maintained an official line that Washington is not at war in the region, it has been retaliating against the Iran-backed groups in Iraq and Syria and carrying out strikes against Yemen’s Houthi military capabilities.

A senior official with the Iran-backed Palestinian militant group Hamas, Sami Abu Zuhri, directly tied the attack to Israel’s campaign in Gaza.

“The killing of three American soldiers is a message to the US administration that unless the killing of innocents in Gaza stops, it must confront the entire nation,” he told Reuters.

“The continued American-Zionist aggression on Gaza is capable of exploding the situation in the region.”

The US military said the attack occurred at a base in northeast Jordan, near the Syrian border.

It did not name the base, but a person familiar with the matter identified it as Tower 22 in Jordan.

US military activity in Jordan can be a sensitive issue, particularly as concern increases about the Israel-Hamas conflict spreading.

The Jordanian government said only that the attack occurred at an “advanced post” along its border with Syria.

Late last year, Amman asked Washington to deploy Patriot air defence systems to bolster its border defence.

It has requested more aid to tackle drones used in a raging multi-billion-dollar drug war along the border with Syria, which Amman blames on pro-Iranian militias who hold sway in southern Syria.

The kingdom has hundreds of US trainers in the country and holds extensive exercises with US troops.