Two missiles were fired at a vessel in an attack southeast of the Yemeni port city of Aden on Thursday, causing a fire onboard, Britain's maritime agency said.

US-led coalition forces are responding to the incident, which took place 70 nautical miles from Aden in the direction of the Red Sea, the United Kingdom Maritime Trade Operations (UKMTO) agency said without elaborating.

"It has been reported that a vessel was attacked by two missiles, resulting in a fire on board," the UKMTO said.

Iran-backed Houthis, who control Yemen's most populous regions, have been attacking vessels in the Red Sea and Bab al-Mandeb Strait in what they say are acts of solidarity with Palestinians in the war in Gaza.

The United States has formed an international coalition to protect maritime navigation in the Red Sea in response to the attacks.