UK headquartered Sibir Energy has said that it has won a court ruling to freeze certain assets of Sibneft over a dispute regarding a joint venture between the two companies and the Priobskoye oil field.

A British Virgin Islands court has ordered a freeze on shares in the Priobskoye field, in which Sibir alleges it was unfairly stripped of its 50% stake by Sibneft and its owner Roman Abramovich.

The UK company said that it held the significant share in the $1 billion rated Priobskoye asset through its joint venture company with Sibneft, Sibneft-Yugra. However, Sibir’s share in the joint venture was illegally diluted from 50% to less than 1% by Sibneft according to legal filings. Sibneft denies the allegations.

The British Virgin Islands court, which was engaged in the dispute after a Russian court threw out Sibir’s claims, has appointed a receiver to take control of the 49% stake in Sibneft-Yugra, according to Sibir. The UK company added that Sibneft and Abramovich have also been ordered to set aside assets worth at least $1 billion until the court-appointed manager takes control of the disputed shares.

We have promised to pursue those responsible for the dilution of our interests, Sibir Energy chief executive officer Henry Cameron said in the statement. We have started proceedings in the British Virgin Islands because BVI companies have been used as vehicles to commit the fraud.