The United States conducted five self-defense strikes in areas of Yemen controlled by the Iranian-backed Houthi militia, U.S. Central Command said Sunday.

It said it struck three mobile anti-ship cruise missiles, one unmanned underwater vessel and one unmanned surface vessel Saturday.

"This is the first observed Houthi employment of a UUV since attacks began in Oct. 23," CENTCOM said in a post on X.

Central Command said it had determined the missiles and vessels presented an imminent threat to U.S. Navy ships and merchant ships in the area.

The Houthi attacks in the Red Sea area have been one sign of spreading conflict in the Middle East since war erupted between Israel and Hamas after the militant Palestinian group's deadly assault on Israel on Oct.7.

The Houthis, who control the most populous parts of Yemen, say their attacks are in solidarity with Palestinians as Israel strikes Gaza. But the U.S. and its allies characterize them as indiscriminate and a menace to global trade.

Faced with mounting Red Sea violence, major shipping lines have largely abandoned the critical trade route for longer routes around Africa. This has increased costs, feeding worries about global inflation while sapping Egypt of crucial foreign revenue from shippers sailing the Suez Canal to or from the Red Sea.