The extension of the contract's duration ensures that the transmission of gas from Russia to Turkey, Greece and other Southeast European countries is carried forward, Transgaz said in a bourse filing on Thursday.
Transgaz did not provide further details.
Russia plans to suspend natural gas exports to Southeast Europe through the Trans-Balkan Corridor, which crosses Ukraine, Moldova, Romania and Bulgaria before reaching Greece and North Macedonia, next year, the Russian ambassador to Serbia, Aleksandr Chepurin, said in March.
As at 11:30 CET on Friday, Transgaz shares traded 0.14% higher at 366.5 lei ($84.9/77.0 euro) on the Bucharest Stock Exchange.
(1 euro = 4.7604 lei)