Russian forces have been accused of "an armed invasion" after units blocked a Ukrainian military airport in the Black Sea port of Sevastopol in Crimea.

Ukraine's new Interior Minister Arsen Avakov hit out as unidentified armed men were patrolling another airport serving the regional capital Simferopol today.

No violence was reported, and flights continued to operate at the airport serving Simferopol.

It was not immediately clear whether the airport in Sevastopol, owned by the Ukrainian defence ministry, was open but there are no scheduled services to the facility.

Russian foreign and defence ministry officials refused to comment.

Avakov wrote in a Facebook post that the Belbek international airport near the Russian naval base in Sevastopol was blocked by military units of the Russian navy.

"I can only describe this as a military invasion and occupation," he said.

Ukraine's Parliament, meanwhile, adopted a resolution calling for a UN Security Council meeting on the crisis and demanding that Russia halt steps which it says are aimed against Ukraine's sovereignty and territorial integrity.

Earlier an Associated Press photographer saw military men armed with assault rifles patrolling Simferopol airport. The men were wearing uniforms without any insignia. Most refused to talk to journalists. One of them, who identified himself only as Vladimir, said they were part of a "self-defence unit" that was making sure that no "fascists" would arrive from Kiev or elsewhere.

On Thursday, masked gunmen with rocket-propelled grenades and sniper rifles seized the parliament and government offices in Simferopol and raised the Russian flag over the parliament building.

Ukrainian officials sharply denounced the move. Ukrainian police cordoned off the area, but didn't confront the gunmen.

The events in the Crimea region have heightened tensions with neighbouring Russia. Moscow scrambled fighter jets to patrol borders in the first stirrings of a potentially dangerous confrontation.

Russia also has granted shelter to Ukraine's fugitive president, Viktor Yanukovych, state media reported, after recent deadly protests in Kiev swept in a new government.

Yanukovych has a news conference scheduled today in Russia's south near the Ukrainian border. He has not been seen publicly since Saturday, and he declared on Thursday in a statement that he remains Ukraine's legitimate president.

Ukraine's parliament elected a new government led by a pro-Western technocrat who promptly pledged to prevent any national break-up.

Moscow has been sending mixed signals about Ukraine but pledged to respect its territorial integrity. Russian President Vladimir Putin has long dreamed of pulling Ukraine, a country of 46 million people considered the cradle of Russian civilisation, closer into Moscow's orbit.

Ukraine's population is divided in loyalties between Russia and the West. Crimea, which was seized by Russian forces in the 18th century under Catherine the Great, was once the crown jewel in Russian and then Soviet empires.

It became part of Ukraine in 1954 when Soviet leader Nikita Khrushchev transferred jurisdiction from Russia, a move that was a mere formality until the 1991 Soviet collapse meant Crimea landed in an independent Ukraine.

In a bid to shore up Ukraine's fledgling administration, the International Monetary Fund has said it is "ready to respond" to Ukraine's bid for financial assistance. The European Union is also considering emergency loans for a country that is the chief conduit of Russian natural gas to western Europe.

Ukraine's finance ministry has said it needs 35 billion dollars over the next two years to avoid default.

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