British energy group BP faced renewed pressure in Russia after a federal court reopened a multibillion-dollar lawsuit filed by minority shareholders over its failed 2011 deal with Rosneft.
The Federal Arbitration Court's move came just days after BP said it was willing to seek a buyer for its half of the TNK-BP oil joint venture it owns with a group of Soviet-born tycoons.
TNK-BP has had a rocky nine-year history and was thrown into fresh crisis last month when its Russian chief executive Mikhail Fridman resigned after saying the firm had become unmanageable because of its disputes.
Some Russian media interpreted the court's decision - issued on Monday and posted on its website on Tuesday - as an attempt by the Russian tycoons to put more pressure on BP to part with its stake on better terms.
The court did not explain why the case had been reopened.
The court case concerns a 409 billion ruble ($A12.7 billion) claim filed by a group of Russian shareholders who own a tiny fraction of one per cent of the stock in TNK-BP Holding.
The group accuses BP of costing TNK-BP unrealised profits when it tried to negotiate a new Arctic oil exploration alliance with the Russian state firm Rosneft.
The Russian tycoons who own half of TNK-BP helped block the deal by arguing that they had priority rights to any new agreement the British firm struck in Russia.
The billionaires deny any link to the shareholders' lawsuit.
The minority shareholders claimed that TNK-BP would have won the Rosneft deal and reaped vast profits in return. But economists said their claims would be impossible to prove in almost any Western court.
A judge in the Siberian district of Tyumen dropped the case in November and the shareholders' appeal had been turned down earlier this year.
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