By Alissa de Carbonnel and Alessandra Prentice
SIMFEROPOL, Ukraine, Feb 28 (Reuters) - Armed men took control of two airports in the Crimea region on Friday in what Ukraine's government described as an invasion and occupation by Russian forces, raising tension between Moscow and the West.
Russia's Black Sea fleet, which is based in the region, denied its forces were involved in seizing one of the airports, Interfax news agency reported, while a supporter described the group at the other site merely as Crimean militiamen.
Amid the confusion over the men's identity, acting president Oleksander Turchinov fired his armed forces chief, while parliament urged Moscow to halt any action that might encourage separatism and asked the United Nations Security Council to discuss the crisis.
Tensions have been rising on the Black Sea peninsula, the only Ukrainian region that has an ethnic Russian majority and the last major bastion of resistance to the overthrow of Viktor Yanukovich as president almost a week ago.
Interior Minister Arsen Avakov accused Russian naval forces of taking over a military airport near the port of Sevastopol, where the Black Sea fleet has its base, and other Russian forces of seizing Simferopol's civilian international airport.
"I consider what has happened to be an armed invasion and occupation in violation of all international agreements and norms," Avakov said on his Facebook page, describing it as a "provocation" and calling for talks.
This met with a Russian denial of involvement in the military airport action. "No Black Sea Fleet units have moved toward (the airport), let alone taking any part in blockading it," Interfax quoted a spokesman for the fleet as saying.
Near the military airport, half a dozen men in camouflage uniforms with automatic rifles were blocking the road using a truck with no licence plates. Reporters were kept from approaching them by volunteer militia, who formed a second road block about 150 metres away.
"Of course they are Russian," said Maxim Lovinetsky, 23, one of the volunteers who manned the post. "They came last night."
Yanukovich is expected to appear before reporters in the Russian city of Rostov-on-Don later on Friday, though President Vladimir Putin has not said whether Moscow will harbour the former leader, who is on the run and wanted by the new government for mass murder after the deaths of protesters in Kiev last week.
In Kiev, the general prosecutor's office said on Friday that Ukraine would ask Moscow to extradite Yanukovich if it is confirmed that he is in Russia.
Ukraine's new rulers have said loans worth $37 billion went missing from state accounts during Yanukovich's three years in power - a jaw-dropping sum even for a population now used to tales of his extravagance and lavish lifestyle, including his opulent residence outside Kiev.
The Swiss government ordered the freezing of the assets of 20 Ukrainians, including Yanukovich and his son Oleksander, Switzerland's financial markets authority FINMA said on Friday.
Police raided the Geneva offices of a Yanukovich firm, while a prosecutor in the city opened a money laundering investigation into the father and son.
Neighbouring Austria has also frozen the local bank accounts of 18 Ukrainians suspected of human rights abuses or corruption, the foreign ministry said, without giving names.
The United States has told Russia to show in the next few days that it is sincere about a promise not to intervene in Ukraine, saying using force would be a grave mistake.
The Kremlin said Putin had ordered his government to continue talks with Ukraine on economic and trade relations and to consult foreign partners including the International Monetary Fund on financial aid.
It also said Putin ordered the government to consider a request from Crimea for humanitarian aid but made no direct reference to the latest events.
Yanukovich provoked protests in Ukraine in November by backing out of plans to sign landmark deals with the European Union and instead saying Kiev would seek closer economic and trade ties with its former Soviet master Russia.
In December, Putin promised Yanukovich a $15 billion bailout, but Russia has put the deal on hold after releasing an initial instalment, saying it wants more clarity about the new government and its policies.
Ukraine's hryvnia currency has been in freefall in recent days as investors worried about Kiev's ability to repay its debts. But with the new rulers seeking IMF help, it bounced back 5 percent to 10.50 per dollar on Friday, according to Reuters data, from the record low of 11 reached on Thursday.
Prime Minister Arseny Yatseniuk said Ukraine hoped to begin receiving international aid soon and was determined to fulfil conditions needed for IMF support. A previous deal collapsed after Kiev failed to implement IMF demands for lower gas subsidies, which would have hurt Ukrainians by pushing up energy prices sharply.
The IMF also wanted a more flexible currency regime, something that has now come about as Kiev gave up this week its attempts to arrest the hryvnia's slide, which had burnt through its dollar reserves. Central bank Governor Stepan Kubiv also said foreign currency withdrawals from bank deposits would be limited to 15,000 hryvnia ($1,500) per day.
ARMED FORCES IN CRIMEA
Kiev's new rulers have said any movement by Russian forces beyond the Black Sea fleet base in Sevastopol would be tantamount to aggression.
But it faces a major challenge in Crimea which was Russian territory until it was transferred to Ukraine in 1954, during the Soviet era. Separatism there has often flared up at times of tension between Moscow and Kiev.
Unidentified gunmen seized the Crimean parliament and raised a Russian flag on Thursday. The gunmen issued no demands and police were casually guarding the building.
Armed men took control of Simferopol airport overnight and were patrolling its grounds on Friday morning.
A Reuters eyewitness at the scene said the men, dressed in full battle gear and carrying assault rifles and machine guns, were moving freely in and out of the control tower.
A man called Vladimir, who said he was a volunteer helping the group, said: "I'm with the People's Militia of Crimea. We're simple people, volunteers ... We're here at the airport to maintain order. We'll meet the planes with a nice smile - the airport is working as normal."
The regional parliament in Crimea managed to hold a session inside the building on Thursday despite the siege, where it voted to stage a referendum on "sovereignty" for Crimea.
Russia's flag still flew from its roof, and lights were on in the windows of its top floor. It was not clear whether the armed men were still inside.
Russia has repeatedly declared it will defend the interests of its citizens in Ukraine, and announced war games on Wednesday near the border, involving 150,000 troops on high alert. Kerry said Lavrov told him the exercises had been pre-planned.
Although Moscow says it will not intervene by force, its rhetoric since the removal of its ally Yanukovich has echoed the run-up to its invasion of Georgia in 2008, when it sent its troops to protect two self-declared independent regions and then recognised them as independent states.