Rescuers pulled three more crew members and a security guard alive from the Red Sea on Thursday, maritime security sources said, a day after Houthi militants sank the Greek ship Eternity C and said they were holding some of the crew still missing.

It was the second Greek bulk carrier sunk this week by the Iran-aligned Houthi militia, shattering months of relative calm off Yemen's coast, the gateway to the Red Sea and a critical route for oil and commodities to the world.

Many shipping companies have suspended voyages due to the fear of attack. The Houthis are believed to be holding six of the Eternity C's complement of 22 crew and three guards, maritime security sources said.

"We remain deeply concerned for the welfare of the crew members in the custody of the Houthis, as well as for those currently unaccounted for," Ellie Shafik, head of intelligence with U.K.-based maritime risk management company Vanguard Tech, said. "Their safety and swift release must be a priority for all involved."

Eternity C was first hit on Monday with sea drones and rocket-propelled grenades fired from speed boats. Four people were believed to have been killed in the attacks, maritime security sources say. If confirmed, the deaths would be the first fatalities in the area since June 2024.

Following a second attack on Tuesday morning, the crew were forced to jump into the water. Rescuers have been searching for survivors since Wednesday morning. The vessel's operator, Cosmoship Management, has not responded to Reuters' requests for comment.

A total of 10 survivors from the Eternity C have been rescued so far — eight Filipino crew members, one Indian and one Greek security guard. The four people rescued on Thursday morning had spent nearly 48 hours in the water.

"This fills us with more courage to continue to search for those missing, as the Greek vessel operator requested, and shows that our search plan was correct," said Nikos Georgopoulos, an official at the Greece-based maritime risk firm Diaplous.

Another 11 people are still missing.

The United States' Mission in Yemen has accused the Houthis of kidnapping crew members and has called for their immediate, unconditional release.

On Wednesday, the Houthis' military spokesperson said in a televised address that the Yemeni navy had "responded to rescue a number of the ship's crew, provide them with medical care, and transport them to a safe location."

Fraught passage

The Eternity C sank on Wednesday, days after Houthis hit and sunk the Magic Seas, reviving a campaign launched in November 2023 that has seen more than 100 ships attacked in what the group said was solidarity with the Palestinians in the Gaza war.

Both of the vessels hit this week flew Liberian flags and were operated by Greek companies. All crew from the Magic Seas were rescued before it went down.

Some of their sister vessels in the respective fleets had made calls to Israeli ports in the past year, an analysis of shipping data showed.

The number of daily sailings through the narrow Bab al-Mandab strait, at the southern tip of the Red Sea and a gateway to the Gulf of Aden, was 32 vessels on July 9 from 43 on July 1, according to maritime data group Lloyd's List Intelligence.

The situation has become so fraught that many of the ships sailing on Thursday broadcast public messages referring to Chinese crew and management or armed guards on board, according to ship tracking data on the MarineTraffic platform. One vessel broadcast a message which said it had no relation with Israel.