SIMFEROPOL, Ukraine (AFP) - Ukraine's ousted pro-Moscow president is set to hold a press conference on Friday after emerging defiant from hiding, as fears grow of a regional conflict in the volatile Crimean peninsula.

Anxious Western governments voiced fears about the "dangerous" situation in Crimea, after dozens of pro-Kremlin gunmen in combat fatigues on Thursday seized government buildings in the autonomous republic, and pleaded with Moscow not to escalate tensions.

News agencies in Moscow said fugitive president Viktor Yanukovych would hold a press conference in Russia on Friday in his first public appearance since fleeing Ukraine at the weekend.

Russian President Vladimir Putin had stoked concerns on Wednesday that Moscow might use its military might to sway the outcome of Ukraine's three-month standoff by ordering snap combat readiness drills near the border with the ex-Soviet state.

Ukraine's interim president Oleksandr Turchynov responded by telling parliament any movement of Russian troops out of their Black Sea bases in Crimea "will be considered as military aggression".

The Russian tricolour was flying over the Crimean parliament and government buildings in the regional capital Simferopol as supporters of Moscow rule flocked in from across the scenic peninsula by car and bus.

The autonomous region's prime minister Anatoliy Mohilyov told AFP up to 50 armed men had seized the buildings and were preventing government workers from going inside.

But his predecessor Sergiy Kunitsyn told lawmakers in Kiev that his local contacts said the raid involved "about 120 well-trained gunmen armed with sniper rifles... and carrying enough ammunition to last them a month."

The gunmen opened the doors to allow in lawmakers who quickly approved the staging of a regional referendum - on May 25 - that would grant Crimea "national sovereignty within Ukraine on the basis of existing treaties and agreements".

The airport of Crimea's capital Simferopol was operating normally early on Friday, an AFP journalist at the scene said, despite reports it had been seized overnight by armed assailants.

Passengers were checking in normally for flights, the journalist said, but about a dozen unidentified armed men could be seen outside the airport perimeter.

Ukraine's bloodiest crisis since its 1991 independence erupted in November when Mr Yanukovych made the shock decision to ditch an EU trade pact in favour of closer ties with old master Russia.

Mr Yanukovych - deposed after a week of carnage in Kiev claimed nearly 100 lives - broke his silence on Thursday by telling Russian news agencies he still viewed himself as president.

The ousted leader, wanted for "mass murder" over the deadly protests, had been widely believed to have gone into hiding in Crimea with his two sons.

But Russian television reported on Wednesday that the 63-year-old was hiding in a government health resort near Moscow.

Mr Yanukovych's statement on Thursday did not disclose his whereabouts but said he was "compelled to ask the Russian Federation to ensure (his) personal security."

Moscow's three main agencies quoted a source in Mr Yanukovych's entourage as saying he would give a press conference in the south-western city of Rostov-on-Don on Friday at 1300 GMT (9pm on Friday Singapore time).

Ukraine has appeared to take a decisive swing back toward the West by ousting Mr Yanukovych and replacing his team with a new brand of younger politicians who will steer the nation - torn between a Russified east and pro-European west - until May 25 presidential polls.

The parliament overwhelmingly confirmed opposition icon Yulia Tymoshenko's top ally Arseniy Yatsenyuk as prime minister and approved the makeup of his untested but strongly pro-Western government.

"Ukraine is being torn apart," a sombre Yatsenyuk said. "But Ukraine sees its future in Europe. We will be a part of the European Union."

Crimea lawmakers agreed to disband the region's government and hand its powers to the heavily pro-Russian parliament.

They also appointed Crimea's Russian Unity party member Sergiy Aksyonov as "prime minister" in place of Mohilyov.

The international response to the standoff was swift and overwhelmingly critical of Russia.

US Vice-President Joe Biden called Mr Yatsenyuk, promising "full" US support as the country's new leaders seek to head off Russian influence.

Defence Secretary Chuck Hagel warned Moscow against any moves "that could be misinterpreted or lead to miscalculation", but it responded by saying it was "strictly adhering" to existing treaties with Ukraine on Russia's Black Sea fleet.

US Secretary of State John Kerry said his Russian counterpart Sergei Lavrov had told him Moscow was not behind the storming of the Crimean government buildings and "will respect the territorial integrity of Ukraine".

Switzerland said on Thursday it was prepared to freeze any funds Mr Yanukovych might have in Swiss banks.