Russian prosecutors say Swiss bank accounts containing some SFr6.2 billion ($4.84 billion) have been frozen as part of a probe into the Yukos oil company.
The announcement comes a week after police carried out raids on companies across Switzerland as part of an investigation into the embattled oil giant.
On Thursday the Russian Prosecutor General said accounts belonging to 20 Russian citizens – including the former head of Yukos, Mikhail Khodorkovsky - had been blocked at their request.
Andrea Sadecky, spokeswoman for Switzerland’s Federal Prosecutor, told swissinfo she could not confirm that bank accounts had been frozen.
“All we can say is that this investigation is being led by the Russian authorities,” she said.
Natalya Vishnyakova, spokeswoman for Russia's Prosecutor General, said the accounts held “personal cash deposits by private individuals somehow or another implicated in the misappropriation of particularly large amounts of state funds”.
“We are investigating the actions of specific individuals who worked at the Yukos oil company,” she said, adding they were accused of “stealing billions of dollars of state funds.”
Russian officials said they would be working with the Swiss authorities to bring about the prosecution of those thought to have “laundered money gained illegally on Swiss territory".
Khodorkovsky has been in jail since late October on charges including fraud and tax evasion. He strongly denied the allegations made by the Russian authorities on Thursday.
Observers claim the probe that led to the arrest is a Kremlin-directed effort to punish Khodorkovsky - Russia's richest man - for funding opposition political parties.
Last week Swiss police raided offices and homes across the country in connection with Russia's Yukos probe on the request of Russian authorities, seizing documents and carrying out interviews.
Officials said the investigation was authorised after receiving a request for international judicial assistance last August from Russian authorities investigating the embattled oil company.
The request named individuals the Russian authorities allege were involved in the fraudulent trade in oil and oil products, and said money from illegal deals was being passed through Swiss companies and bank accounts.
swissinfo with agencies
Russian authorities say Swiss bank accounts containing SFr6.2 billion have been frozen in connection with a probe into the Yukos oil company.
At the centre of the investigation is the former boss of Yukos, Mikhail Khodorkovsky.
Last week Swiss police carried out raids on offices and homes in four cantons in connection with the Yukos probe.
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