BP's billionaire partners in TNK-BP are examining whether the London-based oil major's share swap and arctic exploration deal with Rosneft violates the terms of their partnership, British newspapers reported on Monday.

The Times and Financial Times said AAR, the vehicle by which four Russia-connected oligarchs own half of TNK-BP, had understood the joint venture agreement meant BP would only pursue new ventures in Russia via TNK-BP.

BP and AAR were not immediately available for comment.

BP has had operations in Russia outside of TNK-BP since the joint venture was formed in 2003, including offshore exploration with Rosneft around Sakhalin Island in east Russia.

BP and Rosneft signed their tie-up late on Friday.