Yemen's Iran-backed Houthi rebels launched an explosives-laden sea drone that detonated in international shipping lanes on Thursday, their first use of such a weapon in recent months, a senior US military officer said.
The incident came a day after 12 nations led by the United States warned the Houthis of consequences unless they immediately halted firing on commercial vessels - attacks that the rebels say are in support of Palestinians in Gaza, which Israel has been pounding since October 7.
"A Houthi one-way attack unmanned surface vessel, or USV, detonated in international shipping lanes. Fortunately, there were no casualties and no ships were hit," Vice Admiral Brad Cooper, the commander of US naval forces in the Middle East, told journalists.
The attack was the 25th targeting merchant vessels sailing in the southern Red Sea and Gulf of Aden since November 18, Cooper said.
The United States set up a multinational naval task force earlier this month to protect Red Sea shipping from Houthi attacks, which are endangering a transit route that carries up to 12 percent of global trade.
"Since the operation started, together with our partners, we have shot down 19 drones and missiles and sunk three small boats," Cooper said, but "there are no signs that (the Houthis') irresponsible behavior is abating."
The Houthis say they are targeting Israeli-linked vessels, but Cooper said "our assessment is that 55 nations have direct connections to the ships who've been attacked."
Following Hamas' surprise attack in southern Israel on October 7 - which killed about 1,140 people - the United States rushed military aid to Israel, which has carried out a relentless campaign in Gaza.
Israeli bombardment has killed at least 22,438 people, mostly women and children.
Those deaths have sparked widespread anger in the Middle East and provided an impetus for attacks by armed groups across the region that are opposed to Israel.
US forces in Iraq and Syria have also repeatedly come under fire from drone and rocket attacks that Washington says are being carried out by Iran-backed armed groups.