A US Air Force MQ-9 Reaper drone sits in a hangar at Amari Air Base, Estonia. Reuters

American forces launched "self-defence strikes" Wednesday against Houthi missiles and launch positions in rebel-controlled Yemen that posed threats to commercial shipping and naval forces in the Red Sea, the US military said.

The Iran-backed Houthis, who control much of war-torn Yemen, have been harassing the vital shipping lane since November in a campaign they say is in solidarity with Palestinians in Gaza during the Israel-Hamas war.

Before dawn Wednesday Sanaa time, "US Central Command forces conducted four self-defence strikes against seven mobile Houthi anti-ship cruise missiles and one mobile anti-ship ballistic missile launcher that were prepared to launch towards the Red Sea," CENTCOM said in a statement on social media platform X.

The military said it also shot down a "one-way attack unmanned aircraft system."

"CENTCOM forces identified the missiles, launchers and UAS originating from Houthi-controlled areas of Yemen and determined that they presented an imminent threat to merchant vessels and to the US Navy ships in the region," CENTCOM said.

On Tuesday the Pentagon said a US drone crashed off the coast of Yemen after apparently being struck by a missile fired by Houthi rebels.

The Red Sea attacks have raised insurance premiums for shipping companies, forcing many to avoid the Red Sea, a vital route that normally carries about 12 per cent of global maritime trade.

Agence France-Presse