The venture, TNK-BP, said on Monday that Fridman has submitted a letter of resignation as CEO and chairman of the management board and is due to step down in 30 days. The company did not specify the reason for the resignation.
TNK-BP is owned in equal parts by the British oil giant and a group of Russian billionaire shareholders. The company has been plagued by shareholder conflicts much of the time since it was formed in 2003.
TNK-BP said Monday that it will be managed by "a group of executives who hold powers of attorney related to their areas of responsibility."