International Monetary Fund chief Christine Lagarde urged calm over Ukraine's economic situation on Friday after the country asked for at least $15 billion in financial aid.

"We do not see anything that is critical, that is worthy of panic at the moment," Lagarde said after talks in Washington on Ukraine with German Foreign Minister Frank-Walter Steinmeier.

Dressed in a suit and tie and sitting in front of three Ukrainian flags, Viktor Yanukovych behaved as if he was still Ukraine's leader as he refused to accept the reality of the seismic shift of the last week.

Around 200 journalists found their way to see Yanukovych, 63, make his first appearance in front of the world after his dramatic flight from his country to Russia.

Russian President Vladimir Putin on Friday called for a rapid return to normality in Ukraine and warned against any further escalation of unrest, in telephone calls with key EU leaders, the Kremlin said.

Putin emphasized "the extreme importance of not allowing a further escalation of violence and the necessity of a rapid normalization of the situation," the Kremlin said after Putin had separate phone calls with British premier David Cameron, German Chancellor Angela Merkel and European Union president Herman van Rompuy.

Ukraine's ousted president Viktor Yanukovych on Friday gave a partial and sometimes confusing explanation of his whereabouts since his disappearance last week and how he crossed into Russia.

Yanukovych reappeared in the southern Russian city of Rostov-on-Don on Friday after not being seen in public since February 22.

Pro-Russian activists flexed their muscles in in Crimea on Friday, swarming government buildings after Kalashnikov-toting men in fatigues descended on two key airports, as tensions mounted over the strategic Ukrainian peninsula.

Hundreds of pro-Moscow protesters in Crimea's capital Simferopol massed outside the regional parliament -- seized Thursday by separatist commandos -- as 50 others formed a barricade outside the Ukrainian presidency's local office, blocking its newly designated director from going inside.

Deposed Ukrainian president Viktor Yanukovych insisted Friday in his first public appearance since fleeing to Russia that he had not been overthrown and would continue to fight for the future of Ukraine.

Yanukovych told reporters in the southern Russian city of Rostov-on-Don that he had been "compelled to leave" Ukraine after he received threats to his security.

Germany, France and Poland said they were "deeply concerned" Friday over developments on the volatile Crimea peninsula and called for everything to be done to reduce tensions in Ukraine.

"Everything must be done in order to reduce the tensions in the eastern regions of the country and to promote a peaceful dialogue between all participating powers," the three EU countries' foreign ministers said in a joint statement.

Swiss authorities said Friday they have launched a criminal probe into alleged money laundering by ousted Ukrainian leader Viktor Yanukovych and his multi-millionaire son.

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

U.S. Vice President Joe Biden promised Ukraine's pro-Western interim leaders "full" U.S. support Thursday as they seek to head off Russian influence.

Biden called interim prime minister Arseniy Yatsenyuk to "welcome the formation of a new government in Ukraine," a White House statement said.

The airport in Crimea's capital Simferopol was operating normally Friday, an AFP journalist at the scene said, despite an earlier report that it had been seized overnight by armed assailants.

Passengers had normal access to the airport, on Ukraine's Black Sea coast, and were checking in for flights, the journalist reported.