Russian investigators on Friday charged ex-oil tycoon and Kremlin critic Mikhail Khodorkovsky with organizing the 1998 murder of a mayor in Siberia, ratcheting up their campaign against the exiled former Yukos boss now living in Europe.

"As a result of investigative work, we managed to obtain new information and in light of this, it was decided on December 11, 2015, to prosecute Mikhail Khodorkovsky as a defendant for... the organization of murder," Russia's powerful Investigative Committee said in a statement.

Khodorkovsky, who in an interview with Deutsche Welle last month said Russian President Vladimir Putin's government lacked legitimacy, dismissed the latest charges against him as a sham.

Investigators announced in June that they were reopening a criminal probe into the 1998 murder of Vladimir Petukhov, the mayor of oil-producing city Nefteyugansk, saying that Khodorkovsky -- then the head of the now-defunct oil giant Yukos -- may have ordered the killing.

Khodorkovsky has claimed that the new probe into the mayor's murder, for which his former Yukos security chief is already serving a life term, was ordered personally by Putin.

The Investigative Committee said Friday that Khodorkovsky would be put on a wanted list "in the near future."

Khodorkovsky, once Russia's richest man, spent a decade in prison on charges of tax evasion, fraud and embezzlement, which he blames on a political vendetta by Putin.

In late 2013 he was unexpectedly released and flown out of the country after a presidential pardon but after initially pledging to stay out of politics he has once again become an outspoken critic of Putin. The release followed redoubled German diplomatic efforts in Moscow; Khodorkovsky later chose to take up residency in Switzerland.

On Thursday Russian prosecutors demanded Khodorkovksy be investigated for allegedly calling for "regime change."

bik/msh (AFP, AP)