Russian gas major Gazprom has confirmed that it has put pen to paper on an agreement to buy the 73% share of Sibneft controlled by oligarch Roman Abramovich's holding company.

In its statement, the gas firm said it would pay $13.1 billion to Millhouse Capital, Abramovich’s holding company, which owns 72.663% of oil producer Sibneft.

Following the purchase, Gazprom will own 76% of Sibneft, giving it, and ultimately the Russian government, overall control. The development is the second time inside a year that a major independent Russian energy company has reverted back to state control. Last year Yukos fell back into government hands after a massive retrospective tax bill bankrupted it.

Despite the finalization of the deal between Gazprom and Millhouse Capital, the issue over ownership of Yukos’s 20% holding in Sibneft remains to be resolved. Gazprom’s state sibling Rosneft has claimed the stake while Yukos’s former management argue that it still belongs to the company.