Houthi rebels have launched their first armed maritime drone during the latest assault on commercial shipping in the Red Sea, the US says.

The small seaborne device packed with explosives was launched on Thursday morning but exploded in international shipping lanes a couple of miles from any naval or commercial vessel, said Vice Admiral Brad Cooper, head of US Navy Operations in the Middle East.

He said the drone exploded about 15 miles (24 km) from the Yemen coast and it was unclear which vessel had been targeted.

“We all watched as it exploded,” he told reporters. “Fortunately, there were no casualties and no ships were hit, but the introduction of a one-way attack USV [unmanned surface vessel] is of concern.”

The Iran-backed Houthis have used waterborne attack drones against Saudi-led forces during Yemen’s civil war.

But this is the first time they have been used against Western shipping. The drones have been deployed by Ukrainian forces, including attacks in August on Russian naval ships near the Black Sea port of Novorossiysk, a key hub for the country’s oil exports.

The Houthis have been behind 25 attacks against merchant shipping since the 18 November start of the US-led naval operation Prosperity Guardian, designed to protect ships passing through the Red Sea.

Cooper told reporters that the ships attacked had links to 55 countries through flag state, cargo, ownership or the nationality of crew.

“The impacts of these attacks stretch across the globe … this is an international problem that requires an international solution,” he said.

The five warships currently on the Prosperity Guardian operation have shot down 19 aerial drones and missiles and sunk three small boats, he added.

The choke point of the Bab-al-Mandab strait in the southern Red Sea means vessels are closely packed.

“This, coupled with the fact that Houthi missiles often miss their intended targets, mean that any ship, really at any time, is at risk of collateral damage when passing through the Houthi-controlled territory in the vicinity of the southern Red Sea,” he said.

The seaborne drone was launched just hours after 12 countries demanded an immediate end to the attacks amid warnings of reprisals.