Rescuers pulled six crew members alive from the Red Sea after Houthi militants attacked and sank a second ship this week, while the fate of another 15 was unknown after the Iran-aligned group said they held some of the seafarers.

At least three of the 25 people on board the Eternity C were killed after it was attacked by the Yemen-based group.

The attack on the Eternity C, which also killed at least three of the crew, represents the most serious assault carried out by the Houthis in the crucial maritime trade route.