A currency exchange office in central Moscow. (Agence France-Presse)
Russian authorities said on Tuesday they had placed a top billionaire, Vladimir Yevtushenkov, under house arrest, accusing him of money-laundering.
With a fortune of $9 billion (7 billion euros), Yevtushenkov, the 65-year-old head of Russian holding company AFK Sistema, is Russia's 15th richest man, according to Forbes magazine.
The federal Investigative Committee, which reports directly to President Vladimir Putin, said the tycoon was implicated in money-laundering in connection with the acquisition of shares in oil firm Bashneft.
"Investigation has sufficient grounds to believe that AFK Sistema board chairman Vladimir Yevtushenkov is involved in the legalisation (money-laundering) of property acquired by criminal means," investigators said in a statement.
AFK Sistema -- which holds major interests in Russia's biggest mobile telephone company MTS, travel firm Intourist, the Medsi chain of clinics, and in banking and oil companies -- responded by saying the accusation was "without foundation".
"We are going to use all our energy to contest it," a company spokeswoman, Yekaterina Tsukanova, told AFP.