"Sibir and two of its subsidiaries (the "Sibir Claimants") have commenced proceedings in the High Court in connection with the unauthorized payments that were referred to in its announcement dated 19 February 2009," the release said.
The total amount of the claim currently stands at $328 million, but the company expects it will reach approximately $400 million in due course.
"The proceedings are against former directors, Chalva Tchigirinski and Henry Cameron, Gradison Consultants Inc (a company owned by Tchigirinski) and Derbent Management Limited. Mr Cameron has, as a result of his conduct, been dismissed by the company with immediate effect," Sibir Energy said.
The High Court in London has issued an order to freeze Tchigirinski's bank accounts and assets worldwide ($369 million), as well as assets of Gradison Consultants Inc ($177 million).
Sibir Energy also suspended its shares from trading on the AIM until further notice.
The company has also informed the Financial Services Authority that the price of its shares "may have been manipulated between approximately 16 October 2008 and 31 October 2008" and that "a significant number of the transactions in its shares between those dates were conducted using money that had been taken from the company."
"The launch of the legal proceedings announced today underlines our determination to recover on behalf of our shareholders the funds that were taken from the company," the company's acting CEO, Stuard Detmer, said.
"Our investigation into the events of last year is ongoing and the results will be reported as soon as is practicably possible," he added.
On February 19, Sibir Energy said Tchigirinski's debts were approximately $325 million, not the previously announced $115 million. The company suspended trading in its shares later in the day.
On February 25 the company announced that CEO Henry Cameron had been suspended from all his executive duties pending the result of an investigation into Sibir Energy deals to acquire Tchigirinski's real estate assets.
Sibir Energy was due in December 2008 to consider acquiring various property interests from companies connected with Tchigirinski to prevent him from selling his stake in the company. However, the Moscow government, which holds an 18% stake in the company, objected to the move, saying it might inflict losses on shareholders.
Russian individuals or entities hold 65% of Sibir shares: Chalva Tchigirinsky and Igor Kesaev through a holding company called Bennfield hold 47%, and 18% is held by the Moscow government. Another 25% is in the hands of various financial institutions while the remainder is held by minority shareholders.