Russian ex-nuclear energy minister Yevgeny Adamov has been returned to Moscow from Switzerland, ending an extradition battle.
The United States had also sought Adamov's extradition. The former minister faces fraud charges in both Russia and the US.
The Federal Justice Office confirmed Adamov had been returned to Moscow from Zurich on Friday night accompanied by a Russian police escort.
On Saturday it was reported that he had been jailed and charged with fraud and abuse of power.
Friday's extradition came 24 hours after it was announced that the Swiss Federal Court had overturned a justice ministry decision to send Adamov to the US to answer charges there.
The court in Lausanne, ruling on Adamov's appeal, concluded that the Russian extradition request had priority under international law.
It said the investigation into Adamov's dealings should take place in the country where the crimes are alleged to have taken place.
In September, Swiss justice officials gave precedence to the US request because "had priority been given to Russia, Adamov's Russian citizenship would have meant that he could not subsequently have been extradited forward" to the US.
Adamov's lawyer said the former minister was "delighted and satisfied" with the new ruling.
The Russian government, which condemned the justice ministry's earlier decision to extradite him to the US, also welcomed the court ruling.
But Washington said it was disappointed by the decision. "We respect the Swiss justice system, but we would have greatly preferred that he be extradited here," said State Department deputy spokesman Adam Ereli.
Adamov was arrested by the Swiss authorities on a US warrant on May 2, while visiting his daughter in Bern.
A US federal grand jury in Pittsburgh, Pennsylvania, indicted the Russian on charges of conspiracy to transfer stolen money and securities, conspiracy to defraud the US, money laundering and tax evasion.
US authorities suspect Adamov of embezzling energy department funds and diverting them into private projects in the US, Ukraine and Russia.
In its own extradition demand, Moscow accused Adamov of fraud between 1998 and 2001 during his term of office.
The ex-minister has not denied he put money into private accounts but has said this was normal practice in Russia to shield money from hyperinflation, an unstable banking system and corruption rife after the collapse of communism.
swissinfo with agencies
Yevgeny Adamov was Russia's atomic-energy minister from 1998 to 2001, when a parliamentary commission accused him of corruption.
He is charged by the US with embezzling funds that had been destined for nuclear-safety upgrades in Russia.
Russia had presented a formal extradition request to the Swiss authorities on May 17, accusing Adamov of fraud.