A Moscow court on Thursday ordered the nationalisation of a stake in an oil firm held by a detained oligarch, raising concern about signs of a state-orchestrated grab of assets.

A judge at Moscow’s Arbitration Court ordered the return to the state of the stake held by billionaire Vladimir Yevtushenkov’s holding firm Sistema in oil company Bashneft.

This followed claims by prosecutors that the stake was illegally privatised, Russian agencies reported.

Yevtushenkov is currently being held under house arrest after being dramatically arrested last month on money laundering charges connected to the Bashneft sale, in a move that drew comparisons with the prosecution of former tycoon Mikhail Khodorkovsky.

Russia’s 15th-wealthiest man with a fortune of $9 billion (7 billion euros) according to Forbes, Yevtushenkov has now been reduced to wearing an electronic bracelet.

The probe against him centres on how his holding company Sistema acquired Bashneft and comes after speculation that Russia’s biggest oil producer Rosneft — run by Putin’s loyal lieutenant Igor Sechin — was keen to get its hands on the oil firm.

The judge on Thursday gave Sistema one month to challenge the court ruling, Russian agencies reported.

Sistema is a vast holding which has major interests in the country’s biggest mobile telephone company MTS and a range of other assets.

Yevtushenkov is the most high-profile business figure to fall foul of the authorities since Khodorkovsky, once Russia’s richest man and head of the now-defunct Yukos oil firm, who spent a decade in jail in what his supporters say was revenge for challenging the Kremlin.