Switzerland has granted former Russian oligarch Mikhail Khodorkovsky a one-year residence permit, a government spokeswoman said on Monday, three months after he was released from a Russian jail, according to Reuters.

Once Russia's richest man, the 50-year-old former oil tycoon has made Switzerland his base since he was freed by Russian President Vladimir Putin after serving 10 years in prison for fraud and tax evasion.

Switzerland said it had decided to grant him residency after an application by the Swiss canton, or region, of St Gallen, where his wife lives and where his children go to school. It said there were no political circumstances justifying a refusal of a permit and that it would review his case after one year.

The canton had based its request on important public interests and "significant fiscal interests for the canton", the Swiss migration office said in a statement.

Khodorkovsky has ruled out trying to recover the fortune that made him Russia's richest man, but two multi-billion-dollar law suits involving his defunct oil giant Yukos could be decided this year.

Khodorkovsky, whose oil company Yukos was broken up and sold off, mainly into state hands, has said he will not get involved in politics. He has spent much of the last few months travelling, appearing in the Ukrainian capital Kyiv earlier this month with remarks fiercely critical of Putin.

Switzerland, a popular destination for Russia's wealthy elite, has so far declined to follow the United States and European Union in imposing travel bans and asset freezes on a group of Russian officials over Moscow's annexation of Crimea.