Foreign investors in Russia should tread with caution, the head of BP said on Tuesday amid a dispute between BP and Russia-connected shareholders in their TNK-BP venture.

BP chief executive Tony Hayward also said at a news conference that these shareholders want to tear up an agreement they signed in 2003 to form TNK-BP, the third-largest Russian oil producer.

BP would vigorously defend its rights in the dispute, he said.

TNK-BP CEO Robert Dudley left Russia on Thursday, citing a campaign of harassment as the dispute escalated. His work visa was due to expire on Monday.

Billionaire shareholders in TNK-BP on Monday asked BP to disclose the whereabouts of Dudley, saying his plan to run the firm from abroad could have tax implications.

Dudley is in Central Europe and BP has no tax liability related to his location, Hayward said. It was possible to run TNK-BP from abroad for months, not years, he added.

London-based BP reported second-quarter earnings earlier on Tuesday. - Reuters