The UK-owned Rubymar, attacked by Houthi militants last month, has sunk in the Red Sea, Yemen's internationally recognised government said on Saturday, warning of a "environmental catastrophe" from the ship's cargo of fertilizer.
If confirmed, it would be the first vessel lost since the Houthis began targeting commercial shipping in November, forcing shipping firms to divert vessels on to the longer, more expensive route around southern Africa.
The militants say they are acting in solidarity with Palestinians in Gaza.
On Monday, a Yemeni government team visited the Rubymar, a Belize-flagged cargo ship, and said it was partially submerged. A government statement on Saturday said the ship had sunk in the southern Red Sea on Friday night.
The United States Navy's Fifth Fleet did not immediately respond to a request to confirm the sinking.
The United Kingdom Maritime Trade Operations (UKMTO) agency on Saturday reported a ship sinking, but did not identify it.
The US military previously said the attack had significantly damaged the freighter and caused an 18-mile (29-km) oil slick. The ship was carrying more than 41,000 tons of fertilizer when it came under attack, the U.S. military has said.
Ahmed Awad bin Mubarak, foreign minister in Yemen's Aden-based government, which is backed by Saudi Arabia, said in a post on X: "The sinking of the Rubymar is an environmental catastrophe that Yemen and the region have never experienced before.
"It is a new tragedy for our country and our people. Every day we pay the price for the adventures of the Houthi militia ..."
The internationally recognised government is based in Aden, while the Houthis have gained control of the north and other large centres since a war that began in 2014.
MARINE LIFE THREATENED
The release of some 41,000 tons of fertilizer into the waters of the Red Sea poses a serious threat to marine life, said Ali Al-Sawalmih, director of the Marine Science Station at the University of Jordan.
The overload of nutrients can stimulate excessive growth of algae, using up so much oxygen that regular marine life cannot survive, said Al-Sawalmih, describing a process called eutrophication.
"An urgent plan should be adopted by countries of the Red Sea to establish monitoring agenda of the polluted areas in the Red Sea as well as adopt a cleanup strategy," he said.
The overall impact depends on how ocean currents deplete the fertilizer and how it is released from the stricken vessel, said Xingchen Tony Wang, assistant professor at the Department of Earth and Environmental Sciences at Boston College.
The ecosystem of the southern Red Sea features pristine coral reefs, coastal mangroves and diverse marine life.
"If the ship is salvaged before significant leakage occurs, it may be possible to prevent a major ecological disaster," he said.
Last year, the area avoided a potential environmental disaster when the United Nations removed more than 1 million barrels of oil from a decaying supertanker moored off the Yemen coast. That type of operation may be more difficult in the current circumstances.
The Houthi attacks have stoked fears that the Israel-Hamas war could spread, destabilising the wider Middle East.
The United States and Britain began striking Houthi targets in Yemen in January in retaliation for the attacks on shipping in the Red Sea, Bab al-Mandab Strait and Gulf of Aden.
In a separate report, UKMTO agency said it had received a report of a ship being attacked 15 nautical miles west of Yemen's port of Mokha.
"The crew took the vessel to anchor and were evacuated by military authorities," the UKMTO said in an advisory note.