ATHENS- Greece said on Wednesday it would offer help to Bulgaria after Russia cut off its gas supply, while a Greek official said Sofia had already booked some liquefied natural gas (LNG) shipments to be delivered via a Greek terminal.

Prime Minister Kyriakos Mitsotakis and his Bulgarian counterpart Kiril Petkov discussed the issue by phone on Wednesday.

"The prime minister said that Greece will help Bulgaria to deal with the new situation caused by the Russian decisions on energy," Mitsotakis' office said in a statement, without providing further details.

Russian gas producer Gazprom's said on Wednesday it had halted gas supplies to Bulgaria and Poland for failing to pay for gas in roubles, the Kremlin's toughest retaliation yet to international sanctions over the war in Ukraine.

A Greek source close to the matter told Reuters that Athens could help Bulgaria by reversing the flow of the TurkStream pipeline, a mechanism that has been used before. The pipeline brings in Russian gas to Greece via the Black Sea, Turkey and Bulgaria.

A Greek energy ministry official also said that Bulgaria has already booked some LNG cargoes to be delivered via Greece's Revithoussa LNG terminal off Athens.

Mitsotakis said a long delayed gas link between the two neighbours, the Interconnector Greece-Bulgaria (IGB), should be ready by June, Petkov said.

"He (Mitsotakis) also confirmed joint actions for diversification through liquefied natural gas," Petkov added.

Mitsotakis called an emergency meeting on Wednesday with energy sector representatives to discuss the impact of Gazprom's decision on Greece's gas supply, his office said.

Greece relies on Russian gas for more than 30% of its annual energy needs and its next payment to Gazprom is due in May under a contract that expires in 2026.

Athens has not clarified yet how it will make the payment but it has said that it may be able to indefinitely avoid gas supply problems, even if Russia halts flows.

Under a contingency plan, Greece has said it could get additional liquefied and pipeline gas from Azerbaijan and switch four gas-fired electricity plants to diesel. It will also ramp up coal mining in the next two years as a temporary measure.

(Additional reporting by Renee Maltezou in Athens and Tsvetelia Tsolova in Sofia;)