Houthi attacks in the Red Sea have left three crew members dead and sunk two cargo vessels in a fresh wave of assaults by the Tehran-backed group along the crucial maritime trade route.

Liberian-flagged MV Eternity C sank Wednesday after sustaining "significant damage” and had lost all propulsion, according to the U.K. Maritime Trade Operations (UKMTO), a liaison between the U.K. Navy and commercial shipping. The Houthis claimed responsibility.

U.S. officials said some surviving crew has been kidnapped. "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 U.S. Embassy in Yemen said in a statement, calling for the sailors’ immediate and unconditional release. The Houthi group earlier said it rescued a number of the ship’s crew members, provided them with medical care and transported them to a safe location.