A drone attack on a base in Jordan killed three American troops Sunday, with President Joe Biden blaming Iran-backed fighters and vowing to hold the perpetrators to account, AFP reports.

It is the first time American military personnel have been killed by hostile fire in the Middle East since the start of Israel’s bombardment in Gaza, and the incident will further raise tensions in the region and fuel fears of a broader conflict directly involving Tehran.

“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 the attack, pledging to hold “all those responsible to account at a time and in a manner of our choosing.”

Biden and Vice President Kamala Harris were briefed Sunday afternoon on the attack by several cabinet-level national security officials, the White House said.

Speaking later in the day at a South Carolina church banquet centre, the president doubled down on his pledge of reprisals.

“We shall respond,” the president told the attendees, after holding a moment of silence for the US troops killed in the attack.

US Central Command put the number of wounded from the attack near the Syrian border at 25 and said the identities of those killed will be withheld pending notification of their families.