Yemen's Houthis sank two cargo ships in the Red Sea this week, the first flare-up in seven months in the Iran-backed group's years-long campaign to choke global shipping in protest over the war in Gaza and the plight of the Palestinians.

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.

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