Yemen's Houthi rebels killed 3 mariners with an attack on a ship in the Red Sea, a European naval force says, fueling concern over a possible new wave of attacks by the Iran-backed group.

The attack on the Greek-owned Eternity C follows the Iranian-backed Houthis attacking another vessel on Sunday in the Red Sea that they said subsequently sank.

The Houthis rebels continued an hourslong attack on Liberian-flagged cargo ship in the Red Sea on Tuesday.The Greek-owned Eternity C "remains surrounded by small craft and is under continuous attack," the United Kingdom Maritime Trade Operations center said on Tuesday.