28 May 2012 Last updated at 07:14 ET

TNK-BP chief executive Mikhail Fridman to resign

TNK-BP accounts for a quarter of BP's output

The boss of TNK-BP, the Russian oil group half owned by the UK's BP, is to resign.

BP said Mikhail Fridman, TNK-BP's chief executive, would be stepping down in 30 days "for personal reasons".

TNP-BP is a joint venture between BP and Alfa-Access-Renova (AAR), a group of Russian billionaires that includes Mr Fridman.

Some commentators have suggested that the news marks a further deterioration in the relationship between BP and AAR.

Last year, BP had to abandon plans to form another joint venture with rival Russian oil firm Rosneft after AAR launched a legal challenge.

BP said Mr Fridman's departure would have no impact on TNK-BP because his role had "largely been ceremonial".