Gazprom Neft acted through its 100% subsidiary, Gazprom Neft Finance, to buy the stake in the former subsidiary of the now bankrupt Yukos oil company.
According to unofficial information, the deal, which could be completed this year, is worth some $3.7 billion.
The Federal Antitrust Service approved the transaction on Wednesday.
Tomskneft will produce 11.6 million metric tons (85.5 million bbl) of oil this year, and plans to increase crude output to 13.3 million metric tons (97.8 million bbl) by 2013. The company holds oil and gas production licenses in the Tomsk Region and seven mineral licenses in the Khanty-Mansiisk Autonomous Area in West Siberia.
State-run Rosneft bought a 100% stake in Tomskneft in May 2007 at an auction held to sell Yukos assets. In July, Rosneft said it had sold 50% in Tomskneft to the state-owned VEB bank for $3.4 billion.
However, VEB has always denied the deal, and Rosneft CEO Sergei Bogdanchikov said in early December that his company still controlled 100% in Tomskneft. Sources in Rosneft said that the company was looking for a buyer.
In May Rosneft paid $6.8 billion for a lot of Yukos assets, which included Tomskneft, two oil refineries, a number of oil producing companies and a network of gas stations in the region. This means half of Tomskneft cost Rosneft less than $3.4 billion.
