On Wednesday Gazprom said the merger between the two companies had been finalised, but without Yuganskneftegaz, a former core production unit of the embattled Yukos company, being part of the deal.

Yuganskneftegaz would become an independent state company led by Rosneft head Sergei Bogdanchikov.

Gazprom said that after the merger, Gazprom would get 100% of Rosneft's shares via a share swap, and the government, which already holds 38% of Gazprom, would get 51% of the new joint venture, thus retaining control though allowing foreign ownership of the minority of its shares.

But yesterday Rosneft said the Gazprom statement did not correspond with reality, and should be taken as opinion only.

The exchange scheme "in reality foresees for an exchange of part of Rosneft's shares ... the keeping of Rosneft as an independent legal entity and it keeping full control of the shares that it would transfer to Gazprom," Rosneft said in a statement.

The Russian government has promised to lift a so-called "ring-fence" limiting foreign ownership in Gazprom, seen as one of Russia's most lucrative stocks, after it wins a controlling stake in the merged giant.