Russian investigators have searched homes of several employees of a charity foundation funded by exiled Kremlin critic and ex-tycoon Mikhail Khodorkovsky.

Investigators earlier this month accused Khodorkovsky, who spent 10 years in jail before he was pardoned in 2013, of involvement in the 1998 killing of a Siberian mayor. Once Russia's richest man, Khodorkovsky has dismissed the accusations and ramped up his anti-government rhetoric, accusing President Vladimir Putin of flouting the Russian constitution and leading the country to ruin.

Khodorkovsky's charity foundation Open Russia said on Tuesday that the homes of its employees were raided in connection with a 2003 criminal case which led to Khodorkovsky's jailing. Russia's chief investigative body confirmed the reports.

Open Russia's lawyer Sergei Badamshin said on Twitter that homes of seven employees have been raided.