Russia has accused Ukraine of using naval drones to attack a liquified natural gas carrier off the Libyan coast, which led to its sinking.
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" last 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 north of the port of Sirte," the authority added.
Russia blamed Ukraine for the incident, saying the tanker had been attacked by drones launched from Libya.
"The attack on it was launched from the Libyan coast by Ukrainian naval drones," the Russian transport ministry said.
"We qualify what happened as an act of international terrorism and maritime piracy, a gross violation of the fundamental norms of international maritime law," it added.
The Russian ministry said the carrier was loaded and en route from the northern Russian port of Murmansk.
If confirmed, it would be the first time that Ukraine has attacked a Russian LNG carrier.
All 30 crew members, who were Russian nationals, have been rescued, the Maltese and Russian authorities said.
The Security Service of Ukraine did not respond to a request for comment.
Ukraine has frequently targeted Russian oil refineries and other energy infrastructure in an attempt to deprive Russia's war machine of funding.
The incident adds to the uncertainty on the global markets, already rattled by war in Iran.
Libya's National Oil Corporation said it had no involvement with the LNG carrier, adding that it was on a journey from Murmansk in Russia towards Port Said in Egypt.
"Traffic in Libyan ports continues normally and regularly," it said, adding that the incident had "no impact on the flow of oil and gas supplies or the supply of fuel to the local market".
Meanwhile, a Russian drone hit an empty passenger train in Ukraine's southern Mykolaiv region early this morning, injuring a railway worker, Deputy Prime Minister Oleksiy Kuleba said.
He added that there was also an attempted Russian drone attack on a train operating between the eastern-central city of Dnipro and Kovel in the northwest late yesterday, but it was stopped by railway workers and the drone hit a few metres away from the locomotive.
Ukrzaliznytsia, Ukrainian national railways, said that Russia had intensified drone attacks on railway infrastructure, and that rolling stock was among the main targets.
It reported that 18 strikes had been recorded since the start of March, damaging 41 facilities.
Locomotives, freight cars and specialised equipment used to repair infrastructure have also been targeted, the operator said, and railway depots and bridges had also come under attack this month.
Russian oil supplies
Russia has announced that President Vladimir Putin will meet Hungary's Foreign Minister Peter Szijjarto for talks in the Kremlin on oil supplies.
Hungary is the EU's most Russia-friendly member and has kept up ties with Mr Putin and the Kremlin despite the four-year-long Ukraine offensive.
"I am here to obtain guarantees that, despite the changed circumstances and the global energy crisis, Russia will continue to deliver the necessary quantities of oil and gas for Hungary at unchanged prices," Mr Szijjarto, said in a message on Facebook.
Mr Putin had spoken to Hungarian Prime Minister Viktor Orban yesterday, where the pair discussed the fate of Hungarian citizens captured by Russia while fighting for Ukraine, and the fallout of the war in the Middle East on global energy markets.
Hungary relies on Russian oil and is currently in a standoff with Ukraine over a halt to supplies through the country due to damage to the Druzhba pipeline.
Ukraine said Russia attacked the pipeline and repairs are being held up due to the threat of another strike.
Hungary and Slovakia - which also receives shipments from Russia through the pipeline - accuse Ukraine of delaying the repairs in an attempt to cut them off from Russian supplies.
Kremlin spokesman Dmitry Peskov said buyers of Russian oil were "facing blackmail" and accused Ukraine of "the deliberate blocking of deliveries through the Druzhba pipeline".
