Russian oil giant Rosneft has filed a lawsuit to use a far eastern natural gas pipeline network owned by Gazprom and Western partners, the Ria Novosti news agency reported Monday.
Rosneft is already challenging Gazprom's claim to a monopoly over a planned pipeline to supply Russian gas to China, part of a $400 billion deal to inked between Moscow and Beijing in May.
An Internet site that tracks Russian legal proceedings on Monday showed Rosneft had registered a complaint against Sakhalin Energy, which is half-owned by Gazprom, in a local arbitration court.
The rest of Sakhalin Energy is owned by the Anglo-Dutch group Shell, and two Japanese companies, Mitsui and Mitsubishi.
Ria Novosti quoted a source close to the matter as saying Rosneft is seeking access to a gas pipeline network owned by the Gazprom-led consortium.
Rosneft also reportedly plans to build a competing liquid natural gas (LNG) terminal on Russia's Sakhalin peninsula in partnership with the US group ExxonMobil.
Rosneft, run by President Vladimir Putin ally Igor Sechin, is one of the world's biggest oil companies and it is now looking to muscle into natural gas operations as well.
Gazprom maintains that the pipelines, in which it has invested huges sums of money, only have enough capacity for its own supplies.