Russia's former nuclear energy minister Yevgeny Adamov has been charged with fraud and abuse of office by the authorities in Moscow.
Yevgeny Adamov has denied the charges against him
He was formally charged after being extradited from Switzerland - where he has been held since May - on Friday.
The Supreme Court in Switzerland this week overturned an earlier decision to extradite him to the US, where he is wanted on embezzlement charges.
It is not clear if the charges in Russia relate to the US allegations.
The US accuses Mr Adamov of embezzling up to $9m (£5.2m) it gave to improve security at Russian nuclear facilities.
Washington said it was disappointed with the Swiss decision and called on Russia to see "justice is done".
Mr Adamov was flown to Russia from Zurich airport aboard a specially chartered Russian jet late on Friday, and taken to a Moscow prison.
"Adamov was charged with large-scale fraud and abuse of office in the presence of his lawyer," the Prosecutor-General's Office press secretary Natalia Vishnyakova told Interfax news agency.
She said he would remain in custody.
The former minister's lawyer, Timofei Gridnev, said he would appeal for his client to be freed from custody pending trial, Itar-Tass news agency reported.
Mr Adamov had been held in Bern on a US warrant since May.
Moscow had filed its own extradition request shortly after the US, fearing Mr Adamov's detailed knowledge of the country's nuclear weapons programme could fall into US hands.
The nuclear physicist, who was Russia's atomic energy minister from 1998 to 2001, has accepted his extradition to his homeland but continues to deny the charges.