Russia’s former nuclear minister Yevgeny Adamov must remain in a Swiss prison pending hearings on extradition requests from the United States and Russia.
Switzerland’s Federal Court suspended a decision made two weeks ago by another court ordering Adamov’s release.
Earlier this month the Federal Criminal Court in Bellinzona declared that Switzerland had violated Adamov’s immunity as a former minister when he was arrested in May on a US warrant and said he should be released.
The Federal Justice Office immediately appealed against the ruling and Adamov was kept in custody until the Federal Court in Lausanne reached a decision, which it did on Friday.
"In extradition procedures, the incarceration of the person sought is the rule, from which only exceptional cases should deviate," said the country’s supreme court.
Federal judges still have to decide on whether Adamov’s immunity was violated when he was arrested. But they said that there was no compelling reason to release the former minister until a decision on this had been reached.
Adamov was arrested in the Swiss capital Bern at the beginning of the month at the request of the US authorities.
He stands accused of diverting $9 million (SFr11.5 million) of US funds intended to improve security at Russia’s nuclear facilities when he was atomic energy minister from 1998 to 2001.
However, some experts say that Washington aims to use charges of money laundering, tax evasion and conspiracy to derive valuable information about Russia’s atomic-weapons programme.
On top of the US charges, a Moscow court issued an arrest warrant for Adamov, also for fraud, and formally applied for his extradition.
The US authorities lodged a formal extradition request on Friday. The Swiss government has extradition treaties with both countries and has said it will make its decision "in consideration of all the circumstances".
These include the seriousness and the place where the alleged offences were committed, the dates of the extradition requests, the nationality of the person involved and the possibility of subsequent extradition to another state.
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 $9 million, which had been destined for nuclear-safety upgrades in Russia, and transferring the money to various US companies under his control.
The Americans have filed a demand for his extradition.
Adamov also faces extradition to Russia, which handed a formal request to the Swiss authorities on May 17, on fraud charges.
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