The government also announced it was freezing the assets of 20 Ukrainian officials, including Yanukovych and his son Olexandr and a number of former ministers in his government.

Austria also said it had frozen the assets of 18 Ukrainians suspected of violating human rights and involvement in corruption, but did not give any names.

Yanukovych, 63, is believed to have fled to Russia since being ousted by parliament after the bloody culmination of three months of protests by anti-government demonstrators.

The Swiss government had announced on Thursday that it would freeze any funds Yanukovych had in the country, whose banking secrecy laws are renowned for attracting illicit funds.

The attorney general in Geneva also announced that a prosecutor and the judicial police's financial brigade, as part of a money laundering probe, had launched a raid on Thursday on the offices of a company run by Olexandr.

It is unclear whether Yanukovych himself has funds in Switzerland, but Olexandr opened a branch of his Management Assets Company (MAKO) in Geneva in late 2011.

The 40-year-old dentist and businessman has amassed a personal fortune of around half a billion dollars (some €365 million) in the past three years alone, according to a report in the Swiss weekly L'Hebdo.

His Ukrainian conglomerate reportedly controls nearly half of that country's coal production, and around a third of its electricity production and distribution.

The Geneva branch of the business is run by a businessman of Uzbek origin, who also runs a firm called Partefina, listed with the same address.    

That company is listed as a so-called "family office" — a term used for firms specializing in the management of large family fortunes.

According to L'Hebdo, Partefina is owned by Ukrainian billionaire Rinat Akhmetov, a supporter of Yanukovych who also has offices in Geneva.

Ukrainians had staged demonstrations in the Swiss capital Bern on Wednesday to demand that Switzerland freeze any Yanukovych assets.

Meanwhile, Austria, which has resisted European efforts to improve transparency in the banking sector, is considered in Kiev as a financial safe haven for Yanukovych-linked oligarchs.

The ministry said the move was taken as a preliminary security measure until targeted sanctions that the European Union agreed to slap on Ukrainians take effect.

The bloc on February 20th agreed to a travel ban and asset freeze on Ukrainians with "blood on their hands" amid worsening violence in Kiev, but did not name those affected and said the number would depend on developments.