A Russian-flagged tanker carrying liquefied natural gas has erupted in flames before sinking in the Mediterranean Sea, Libyan authorities say.
Russia asserted that an attack by Ukrainian sea drones was to blame.
The Libyan Maritime Authority reported "sudden explosions, followed by a massive fire" on the Arctic Metagaz on Tuesday, when it was about 240km off the city of Sirte.
The tanker, carrying 61,000 tons of LNG, "completely sank" between Libya and Malta, a statement said.
All 30 crew members were rescued and put on another vessel heading to the Libyan city of Benghazi, it said.
Russia's transport ministry said the vessel was hit by Ukrainian sea drones launched from the Libyan coast.
Russian President Vladimir Putin on Wednesday evening called what happened to the tanker "a terrorist attack" that "exacerbates the situation on global energy markets, including gas markets".
Ukrainian officials made no immediate comment on the accusation.
Previous Ukrainian attacks on Russian ships have reportedly come from the Libyan coast although officials in Kyiv have not publicly confirmed those reports.
In the past, Ukraine's military has said it used sea drones to sink Russian vessels in the Black Sea as part of efforts to combat Russia's full-scale invasion which began just over four years ago.
Last October, Ukraine's state security service unveiled an upgraded sea drone, called the Sea Baby, which it said had a range of 1500km and could carry a warhead up to 2000 kilograms.
The tanker that sank was under sanctions, suspected to be part of Russia's shadow fleet of energy tankers trying to bypass sanctions imposed on Russia over its war in Ukraine.
The Metagaz had sailed from the northwestern Russian city of Murmansk on the Barents Sea and was bound for Port Said in Egypt, on the Mediterranean, the Libyan Maritime Authority said.
Its last reported position was in the western Mediterranean off the coast of Malta, according to MarineTraffic, a ship-tracking platform.
Egypt denied any links to the vessel and said the tanker was not en route to any Egyptian port, according to a statement by its petroleum ministry on Wednesday evening.