The Houthi movement in Yemen says it has struck a US merchant ship in the Red Sea in a fresh attack targeting commercial shipping.
It named the ship as the KOI, which it said was US-operated.
Maritime security firm Ambrey said a vessel operating south of Yemen's port of Aden had reported an explosion on board but it did not name the ship.
Meanwhile, the US has launched new air strikes in Yemen, targeting 10 drones reportedly being set up to launch.
According to Reuters news agency, the KOI is a Liberian-flagged container ship operated by UK-based Oceonix Services. The same company's fleet includes the oil tanker Marlin Luanda, which was damaged by a missile on Saturday.
The Houthis regard all Israeli, US and British ships as legitimate targets following Israel's war on Hamas in Gaza, and US and British targeting of Houthi missile positions in what the two countries say are efforts to protect commerce.
Houthi military spokesperson Yahya Sarea said on Wednesday that the movement's armed forces had targeted an American merchant ship named KOI with "several appropriate naval missiles".
The ship, he said, had been heading to "the ports of occupied Palestine", a phrase which is sometimes used to mean Israel.
Yemen, he added, would "not hesitate" to retaliate against "British-American escalation".
"All American and British ships in the Red and Arabian Seas are legitimate targets for the Yemeni Armed Forces as long as the American-British aggression against our country continues," the Houthi spokesman said.
US Central Command said the 10 drones being prepared for launch in Yemen had posed a threat to merchant vessels and US warships in the region.
All 10 were destroyed along with a Houthi drone ground control station, it said.
The US added that one of its warships had shot down three Iranian drones and a Houthi anti-ship ballistic missile in the Gulf of Aden.
Houthi attacks on shipping in the Red Sea have slowed down international trade, raising fears of supply bottlenecks.
On 7 October, hundreds of Palestinian gunmen from Gaza infiltrated southern Israel, where they killed around 1,300 people - mostly civilians - and took 250 others hostage.
Israel responded by launching a military campaign in Gaza, during which more than 26,900 people - most of them women and children - have been killed, according to the health ministry there which is controlled by the Hamas group.
