Russia's Sistema chairman under house arrest - investigators

"Investigators have reasonable grounds to believe that Sistema Board Chairman Vladimir Yevtushenkov is involved in the legalisation of property acquired by criminal means. Today he was accused of money-laundering," the Investigative Committee said in a statement on its website.

Sistema, which also controls Russia's biggest mobile phone operator MTS, declined to comment.

Sistema had been earlier restricted from selling shares in Bashneft due to an investigation that Sistema had said it was not party to.

The court ruling hampered plans for a share offering by the mid-sized oil company in London. Bashneft has been planning a market float since it was acquired by Sistema in 2009.

Since Sistema became the majority shareholder, Bashneft has shown one of the highest production growth rates among Russian oil companies thanks to advanced recovery techniques used at its deposits.

Russian business daily Vedomosti reported in June that state-controlled Rosneft, Russia's biggest oil producer run by President Vladimir Putin's ally Igor Sechin, was interested in buying Bashneft.

But Yevtushenkov told Reuters at the time Sistema, which occupies an historic building in front of the Kremlin's walls, was not involved in negotiations to sell Bashneft to Rosneft, while Rosneft would not comment on the report.

Yevtushenkov is ranked Russia's 15th richest man by U.S. magazine Forbes with an estimated fortune of $9 billion (£5.5 billion).

(Reporting by Maria Kiselyova; editing by Keiron Henderson and Susan Thomas)