Libyan authorities said on Wednesday that the "Arctic Metagaz" tanker had sunk in the Mediterranean Sea between their coast and nearby Malta.
A Russian LNG tanker caught fire off the coast of Libya, with all 30 crew members on board the vessel unharmed and rescued, Moscow said.
The Libyan port authority said the carrier sunk after "sudden explosions" north of the port of Sirte.
The Arctic Metagaz tanker "had experienced sudden explosions followed by a massive fire, which ultimately led to its complete sinking" on Tuesday night, the authority said.
"The wreckage occurred in the maritime area between Libya and Malta, within the Libyan search-and-rescue zone ... approximately 130 nautical miles (240 kilometres) north of the port of Sirte," the authority added.
The ship had issued several distress calls late on Tuesday to port and naval authorities. Malta’s armed forces said they had received a distress message from the vessel and were able to geolocate it.
The vessel, suspected to be part of the Kremlin’s shadow fleet of energy tankers evading Western sanctions, last reported its position as sailing off the coast of Malta, according to ship tracking data platforms.
Authorities did not detail the nationalities of the crew members on board the vessel.
Meanwhile, Russia has accused Ukraine of attacking the tanker from the Libyan coast by naval drones, according to a statement by Russia’s transport ministry. The vessel was loaded and en route from the northern Russian port of Murmansk, according to Moscow.
Ukraine's military has not yet commented on the reports.