Houthi rebels in Yemen have launched a violent new wave of attacks on ships in the Red Sea, sinking two vessels and killing crew members.

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.

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