Yemen's Houthi rebels continued an hourslong attack Tuesday targeting a Liberian-flagged cargo ship in the Red Sea, authorities said, after the group claimed to have sunk another vessel in an assault that threatens to renew combat across the vital waterway.

A Liberian-flagged cargo ship came under fire on Monday in the Red Sea, with two security guards on board reportedly hurt and two others missing in an assault that came after Yemen's Houthi rebels purportedly sunk another vessel in a similar attack.

Yemen’s Iran-aligned Houthis said on Monday that a cargo ship they struck with gunfire, rockets and explosive-laden remote-controlled boats had sunk in the Red Sea, after their first known attack on the high seas this year.