Eleven crew members remained missing on Thursday after Yemen's Houthi militants attacked and sank a cargo vessel in the Red Sea, with United States officials warning the group may have kidnapped survivors.

Ten crew members of the Liberian-flagged Eternity C had been rescued as of Thursday, while at least four others had died, according to security teams involved.

The Greek-owned vessel was first attacked on Monday with sea drones and rocket-propelled grenades from Houthi speedboats, and then again on Tuesday night, forcing crew members to abandon ship in what US officials called a dangerous escalation of the rebels' campaign against vessels linked to Israel.

Security company Ambrey reported the Eternity C sank on Wednesday, near the Houthi-controlled Yemeni port of Hodeidah after sustaining severe damage.

The sinking followed Sunday's attack on another Liberian-flagged and Greek-owned vessel, the Magic Seas, marking an intensification of Houthi strikes in the Red Sea that the Iran-aligned rebels claim are linked to the Israel-Hamas conflict in Gaza.

Expressing solidarity with Palestinians in Gaza, the Houthis claimed responsibility for attacking the Eternity C, which they said was heading to Israel's Eilat port.

"The naval force of the Yemeni armed forces targeted the ship," their military spokesperson, Yahya Saree, said.

According to the European Union's naval mission in the Red Sea, the Eternity C's 25-member crew included 21 Filipino sailors, one Russian, and three security personnel.

One Russian and three Filipinos were killed in the attack, maritime security sources said.

Those rescued included eight Filipino crew members, one Indian, and one Greek security guard. Seven of the seafarers were rescued on Wednesday, while those found on Thursday had spent more than 48 hours in the water.

Houthi-released footage showed rebels offering an escape to the crew over the radio, but it remained unclear whether more crew members fled, or what happened to them.

The group claimed its forces "responded to rescue a number of the ship's crew", but provided no details about numbers or location, The Associated Press reported.

The US embassy in Yemen, which has been operating from Saudi Arabia since 2015, posted on X late on Wednesday that the Houthis had "kidnapped" the crew.

"After killing their shipmates, sinking their ship and hampering rescue efforts, the Houthi terrorists have kidnapped many surviving crew members of the Eternity C," the embassy said.

"We call for their immediate and unconditional safe release."

If they have been detained, it would not be the first time Houthis had detained sailors. After seizing the Galaxy Leader vessel in November 2023, they held the crew until January 2025.

Deep concern

China's deputy UN representative, Geng Shuang, on Wednesday urged the Houthis to stop targeting commercial vessels in the Red Sea and expressed "deep concern" about the recent attacks.

Speaking at the Security Council, Geng urged respect for international maritime law while emphasizing that Red Sea's stability depends on broader regional peace, reported Xinhua news agency.

He called on the international community to step up humanitarian assistance to Yemen, and said that the recent ceasefire agreement between Israel, the United States, and Iran, should be observed, adding that state sovereignty should be respected and UN Charter principles adhered to.

On the Gaza conflict, the Chinese envoy said: "The war in Gaza should stop at an early date. The humanitarian catastrophe in Gaza should come to an end at an early date. The two-state solution should be implemented at an early date."

Geng emphasized that a lasting solution to issues in the Red Sea and in Yemen require easing and de-escalation of the overall situation in the region.