The Houthis have been targeting Israel-linked vessels transiting the vital Red Sea trade route for months to pressure Israel to halt its war and siege of Gaza, which has killed more than 30,000 Palestinians and reduced most of the territory to rubble.

But Wednesday's deaths appear to be the first fatalities resulting from the Houthi offensive.

An anti-ship ballistic missile struck the Barbados-flagged, Liberian-owned M/V True Confidence, after which its crew reported "three fatalities, at least four injuries, of which three are in critical condition, and significant damage to the ship", the US Central Command (CENTCOM) said in a statement.

"The crew abandoned the ship and coalition warships responded and are assessing the situation," it said, noting that the attack was the fifth time the Houthis had launched an anti-ship ballistic missile in two days.

The Philippine government's Department of Migrant Workers said in a statement on Thursday that two of the crew members killed were Filipinos and two others were "severely injured".

Houthi military spokesman Yahya Saree wrote on social media that the True Confidence was targeted with multiple missiles "after the ship's crew rejected warning messages" from the Houthis.

US military strikes
 

CENTCOM said several hours after the True Confidence was hit that it had carried out strikes against "two unmanned aerial vehicles in a Houthi controlled area of Yemen that presented an imminent threat to merchant vessels and U.S. Navy ships".

"These actions are taken to protect freedom of navigation and make international waters safer and more secure for U.S. Navy and merchant vessels," it said in a separate statement without elaborating.

The United States and Britain have launched repeated strikes on Yemen since January in response to the Houthi offensive but the rebels have continued to target merchant vessels.

The British embassy in Sanaa said earlier the death toll on board the True Confidence was at least two, describing the loss of life as "the sad but inevitable consequence of the Houthis recklessly firing missiles at international shipping".

British Foreign Secretary David Cameron promised that "we will continue to stand up for freedom of navigation and back our words with actions".

The Houthis began attacking ships in the Gulf of Aden and the Red Sea in November, a campaign they say is intended to signal solidarity with Palestinians in Gaza.

They have vowed to strike Israeli, British and American ships, as well as vessels heading to Israeli ports, disrupting traffic through the vital trade route off Yemen's shores.

The latest incident comes after a Belize-flagged, Lebanese-operated ship sank on Saturday with 21,000 metric tonnes of ammonium phosphate sulfate fertiliser on board.

The ship, called the Rubymar, had been taking on water since it was hit by a Houthi missile on February 18 that damaged its hull and forced the evacuation of its crew to Djibouti.

The Houthi offensive has caused several major shipping firms to suspend passage through the Red Sea, which usually carries around 12 percent of global trade.

Egypt says that the Suez Canal's revenues have decreased by 40-50 percent since the beginning of the Israeli war on Gaza and the ensuing Red Sea tensions.

*This story was edited by Ahram Online