Mr Khodorkovsky, 52, showed defiance after the authorities said they would charge him with the murder, insisting it won't be long before President Vladimir Putin is ousted from power. The former Yukos Oil chief was freed by presidential pardon in December 2013 after serving a decade in prison on fraud, tax- evasion and money-laundering charges that he says were retribution for funding opposition parties. After pledging to steer clear of politics, he's been supporting efforts to end Putin's 15-year rule.

Russian President Vladimir Putin in Sochi last month. Credit:EPA

The Investigative Committee's spokesman, Vladimir Markin, told the state-run TASS news service that the raids on Tuesday were in connection with a 2003 criminal case involving Yukos. At the time of the case, which centred on accusations that Mr Khodorkovsky and others had misappropriated shares in a fertiliser producer, Apatit, some of Open Russia's staff were children, the group said.

Investigators are also checking the legality of the acquisition of Yukos shares by foreign companies that initiated proceedings in international courts to enforce a $US50 billion ($69 billion) damages award against Russia, the committee said on its website. The Permanent Court of Arbitration in The Hague ruled in 2014 that Russia was liable to pay the sum for the seizure of Yukos assets.

The move marks a "ridiculous" effort to counter the enforcement of the damages in United States and other courts by securing a ruling in Russia that declares the original acquisition of the Yukos shares illegal, said Tim Osborne, head of GML, a holding company belonging to four former owners of Yukos who don't include Khodorkovsky.