Picture used for illustrative purposes only.

A bulk carrier sank days after an attack by Yemen's Houthi rebels believed to have killed one mariner on board, authorities said early Wednesday, the second-such ship to be sunk in the rebel campaign.

The sinking of the Tutor in the Red Sea marks what appears to be a new escalation by the Iranian-backed Houthis in their campaign targeting shipping through the vital maritime corridor over the Israel-Hamas war in the Gaza Strip.

The attack comes despite a monthslong US-led campaign in the region that has seen the Navy face its most-intense maritime fighting since World War II, with near-daily attacks targeting commercial vessels and warship.

The Liberian-flagged, Greek-owned-and-operated Tutor sank in the Red Sea, the British military's United Kingdom Maritime Trade Operations center said in a warning to sailors in the region.

"Military authorities report maritime debris and oil sighted in the last reported location,” the UKMTO said. "The vessel is believed to have sunk.”

The Houthis did not immediately acknowledge the sinking. The US military as well did not immediately acknowledge the sinking and did not respond to requests for comment.

The Tutor came under attack about a week ago by a bomb-carrying Houthi drone boat in the Red Sea. John Kirby, a White House national security spokesman, said Monday that the attack killed "a crew member who hailed from the Philippines.” The Philippines has yet to acknowledge the death, but the man who had been aboard the Tutor has been missing for over a week in the Red Sea, which faces intense summertime heat.

The use of a boat loaded with explosives raised the specter of 2000’s USS Cole attack, a suicide assault by Al Qaida on the warship when it was at port in Aden, killing 17 on board. The Cole is now part of a US Navy operation led by the aircraft carrier USS Dwight D. Eisenhower in the Red Sea to try and halt the Houthi attacks, though the rebels continue their assaults.

The Houthis have launched more than 50 attacks on shipping, killing four sailors. They've seized one vessel and sunk two since November, according to the US Maritime Administration. A US-led airstrike campaign has targeted the Houthis since January, with a series of strikes May 30 killing at least 16 people and wounding 42 others, the rebels say.

Associated Press