Sibir accuses Sibneft of illegally diluting its holding from 50 percent to less than 1 percent by secretly selling shares in the joint venture, called Sibneft-Yugra, to companies affiliated to Sibneft. Sibneft has denied any wrongdoing and said it acted within broad agreements between the venture's shareholders. Sibir Energy is controlled by Shalva Chigirinsky, a construction and oil magnate who Forbes magazine said in May was worth $470 million. Sibneft has also said it is incredible that Sibir claims not to have discovered the dilution until a year after it took place, despite the importance of the asset. On Monday, Sibir said in a statement that the court had frozen the disputed stake until a further hearing, to take place on or before July 27. The court appointed a receiver to take control of the 49 percent stake while the case continues. The court said Abramovich, whom Forbes named as Russia's richest man, with a $14.7 billion fortune, had to maintain assets of at least $1 billion until the receiver had control of the 49 percent stake. PIN/Reuters