The Swiss authorities have frozen all assets of Ukraine's deposed president, Viktor Yanukovych, and launched a money laundering investigation into him and his son.
The foreign ministry said all assets and bank accounts held by Yanukovych and 19 other people of his entourage in Switzerland were blocked.
The government wished to take "all measures necessary to avoid the risk of any misappropriation of financial assets of the Ukrainian state," a statement said.
The aim was "to prevent these assets being taken out of Switzerland before they can be blocked through the ordinary channels of mutual legal assistance".
No details were released on the amount of assets affected by the freeze.
The statement reminded banks that they should be more cautious in handling Ukrainian funds in Switzerland.
The government made its decision without first receiving a request from the interim government in Kiev. The foreign ministry said it was too early to name a figure in relation to the assets.
Last week, Switzerland banned the export of arms and ammunitions to Ukraine.
Friday's move by the Swiss government came as neighbouring Austria and the principality of Liechtenstein announced a similar asset freeze. The European Union has also agreed such measures, but they are still to come into force.
On Thursday, Geneva's chief prosecutor's office searched the premises of a company owned by Oleksander Yanukovych and removed documents.
The prosecutor's office said it was investigating charges of "aggravated money laundering".
No further details on the investigation were immediately available.
Yanukovych has been on the run since he was driven out of Ukraine's capital nearly a week ago following three months of protests over his pro-Russia stance.
He gave a news conference in the southern city of Rostov-on-Don on Friday in his first public appearance since last week.
Ukraine's new prime minister Arseny Yatseniuk accused the Yanukovych government of stripping state coffers bare, saying $37 billion (CHF33 billion) of credit it had received had disappeared. He warned that unpopular measures would be needed to save the economy.
OSCE in Crimea
Meanwhile, Organization for Security and Co-operation in Europe (OSCE), chaired by Switzerland in 2014, has expressed its serious concern at the ongoing developments in Crimea.
Western nations have called on Russia to ease tensions in Ukraine's southern autonomous region on the Black Sea after armed men seized the local parliament and raised the Russian flag.
In a statement on Thursday, Swiss Foreign Minister Didier Burkhalter announced a visit by his personal envoy, Swiss diplomat Tim Guldimann, and the OSCE High Commissioner on National Minorities, Astrid Thors, within the coming days.
"I urge everyone concerned to exercise responsibility and caution in this precarious situation, and call on all sides to take all necessary measures to avoid further escalation and refrain from violence," Burkhalter said.
swissinfo.ch and agencies