SIMFEROPOL, Ukraine - Pro-Russian activists flexed their muscles 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.

And in the port city of Sebastopol, home to Russia’s Black Sea Fleet, 40 pro-Russian Cossacks ripped down the Ukrainian flag flying over city hall, cheered on by hundreds of supporters.

The displays of pro-Russian fervour came after Ukraine’s new pro-Western government accused Russia of launching an “armed invasion” of Simferopol’s airport and another near Sebastopol.

Ukrainian authorities later said they had regained control of the airports, and a spokesman for Russia’s Black Sea Fleet denied any involvement.

But AFP reporters said dozens of men in battle fatigues and armed with Kalashnikovs continued to encircle the Simferopol airport. The armed men’s heavy military equipment showed the risk of tensions escalating into conflict on the peninsula, where ethnic Russians are a majority and pro-Moscow sentiment runs high. Armed with machine guns, the men looked ready for battle in full combat uniform, wearing flak helmets and bullet-proof vests as they checked all incoming and outgoing traffic.

They refused to speak to journalists, and it was not immediately clear what army or paramilitary group they belonged to. Unarmed pro-Russian activists nearby said the armed men had arrived in the middle of the night following rumours that members of the new government were planning to fly in.

The activists said they were “volunteers” there to maintain order.

“We’re here to prevent fascists or radicals from western Ukraine from coming here by plane,” said Vladimir, 46, a former military officer dressed in an army jacket.

Meanwhile, ousted Ukrainian President Viktor Yanukovich, appearing in public for the first time since he fled from Ukraine to Russia, said on Friday he would not give up the fight for his country’s future.

In the southern Russian city of Rostov-on-Don, he told reporters he had been forced from power by “nationalist, pro-fascist gangsters” and blamed the crisis on the West for “indulging” protesters seeking his overthrow.

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.

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.