A drone and speedboat attack off Yemen killed four seafarers on a Liberian-flagged, Greek-operated bulk carrier, an official with knowledge of the matter said on Tuesday, the second incident in a day, following months of calm, EDnews reports, citing Reuters.

Traffic in the Red Sea, a key waterway for oil and commodities, has dropped since Yemen's Houthi militia aligned with Iran began targeting ships in 2023 in what it called solidarity with Palestinians under assault in Israel's war in Gaza.

The deaths on the Eternity C, the first involving shipping in the Red Sea since June 2024, take to eight the total of seafarers killed in the Red Sea attacks.

One more injured crew died on board after the attack, a source with knowledge of the matter said, speaking on condition of anonymity.

The Houthis have not commented on the Eternity C, but hours earlier claimed responsibility for a strike on another Liberia-flagged, Greek-operated bulk carrier, the MV Magic Seas, off southwest Yemen on Sunday, saying the vessel sank.

"After several months of calm, the resumption of deplorable attacks in the Red Sea constitutes a renewed violation of international law and freedom of navigation," IMO Secretary-General Arsenio Dominguez said on Tuesday.

The US State Department condemned the "unprovoked Houthi terror attack on the civilian cargo vessels MV Magic Seas and MV Eternity C", as demonstrating the threats the Houthis posed to freedom of navigation and regional security.

Washington "will continue to take necessary action to protect freedom of navigation and commercial shipping," it added in a statement.