US forces destroyed a Houthi underwater drone on Saturday, making this the first known instance of the Yemeni rebel group employing such a device.

The news will add to the concerns of international shipping operators, that have cut transits through the Red Sea by half since the Houthis began attacking commercial vessels off Yemen’s waters.

“This is the first observed Houthi employment of a UUV [unmanned underwater vessel] since [Houthi] attacks began on 23 October,” the US Central Command (Centcom) said in a situation report on its activities for 17 February.

The Houthis are already known to be employing drones operating on the sea’s surface and one such device was detected and destroyed on Saturday — as was the UUV and three mobile anti-ship cruise missiles.

The US military detected and destroyed all five objects in Houthi-controlled areas of Yemen.

“Centcom … determined they presented an imminent threat to US Navy ships and merchant vessels in the region,” the military command said.

The Houthi rebel group, which controls large swathes of Yemen, has attacked more than 50 vessels since November, as part of a policy to pressure Israel to stop the war it wages in Gaza.

Its declared targets are ships linked to or trading with Israel or belonging to companies in the US and the UK, whose forces have been bombing the Houthis in retaliation.

The campaign has been highly effective in disrupting ship traffic through the Red Sea and the Suez Canal. According to Portwatch, a website run by the IMF and the University of Oxford, the seven-day moving average of ship transits through the water dropped to 41 on 13 Feb, down from 75 two months before.