Shares in one of Russia’s biggest oil companies have been frozen by prosecutors investigating fraud allegations against its chief executive.
The Moscow stock market suffered its second nosedive in a week on the back of the announcement.
The market’s sharp reaction appeared to reflect investor fears that a probe of Yukos that began in July could foretell troubles for Russia’s biggest companies.
The freeze on 44 percent of Yukos shares came as Russian news agencies reported President Vladimir Putin had signed an order relieving Chief of Staff Alexander Voloshin from duty.
Rumours that Mr Voloshin had resigned had rattled Russian political and business circles for several days.
Mr Voloshin reportedly tendered his resignation after Saturday’s arrest and jailing of Mikhail Khodorkovsky, the head of the Russian oil giant Yukos.
The arrest has been widely seen as an action staged by some of President Putin’s top lieutenants to avenge the tycoon’s political activities, which include funding of opposition parties.
Mr Voloshin, 47, held the third ranking post in the Russian hierarchy and was seen as an advocate of liberal reform and big business interests.
The prosecutor general’s office said it had sequestered 44.1 percent of shares in Yukos owned by its holding company, but denied the aim was to strip Mr Khodorkovsky of his dominant stake in Russia’s largest oil producer.
Mr Putin met top Western investors in Russia for more than 90 minutes in the Kremlin to assure them that he was keen to protect investor rights, and that an investigation into Yukos did not mean that the government was out to get big business.