A crude oil tanker has reported four attacks off Yemen's port of Mokha during the last 24 hours, the United Kingdom Maritime Trade Operations agency said on Friday, and the vessel's manager said the ship and its crew were safe.

Yemen's Iran-aligned Houthi militants have launched attacks on international shipping in the Red Sea region since November in solidarity with Palestinians in the war between Israel and Hamas.

On Thursday, the captain of the Delta Blue tanker reported that two small craft had approached and fired a rocket-propelled grenade which exploded near the Liberia-flagged vessel some 45 nautical miles south of Mokha.

Each of the two small boats had four people on board, the UKMTO agency said. Hours later, another missile exploded close to the tanker.

On Friday, the UKMTO said the vessel had reported another attack by an uncrewed surface vessel and one by a missile that landed near the ship.

Asked about the incidents, Athens-based Delta Tankers told Reuters the crew and vessel were safe.

"The vessel is continuing on its onward journey," the Delta Blue's manager added.