"He knows secrets, of course, but he has not given any to anyone and he will not," Bulat Nigmatulin, the head of scientific research at Russia's centre for nuclear station safety, told Echo Moscow radio.

"He is a citizen and there can be no question of him giving up secrets."

The arrest May 2 of Yevgeny Adamov, a former Russian energy minister, in Switzerland on a US warrant on suspicion of fraud and money laundering provoked a sharp reaction in Russia. Media reports and some politicians have raised fears that Adamov, who held the portfolio from 1998-2001, could give US investigators information about Russia's nuclear programme.

A subsequent extradition request by Russia to Switzerland last week was widely interpreted in the media as an attempt to undercut the US extradition and rescue Adamov.

"The Russian side must do everything possible so that Adamov gets to Russia," Nigmatulin said. "Adamov must return to Russia and if there are criminal charges, face a court."

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