Witnesses told the Interfax news agency that the 50 or so men were wearing the same gear as the ones who seized government buildings in the city, Simferopol, yesterday and raised the Russian flag.
The report said the men with "Russian Navy ensigns" first surrounded the Simferopol Airport's domestic flights terminal. The report could not be immediately confirmed. A woman who later answered the phone at the airport said "no comment," and the airport's website listed the morning's first flight, to Moscow, as boarding on schedule.
The events in the Crimea region have heightened tensions with neighboring Russia, which scrambled fighter jets to patrol borders in the first stirrings of a potentially dangerous confrontation reminiscent of Cold War brinksmanship.
Russia also has granted shelter to Ukraine's fugitive president, Viktor Yanukovych, after recent deadly protests in Kiev swept in a new government.
While the government in Kiev, led by a pro-Western technocrat, pledged to prevent any national breakup, there were mixed signals in Moscow. Russia pledged to respect Ukraine's territorial integrity.
Yanukovych was said to be holed up in a luxury government retreat, with a news conference scheduled today near the Ukrainian border. He has not been seen publicly since Saturday.
As masked gunmen wearing unmarked camouflage uniforms erected a sign reading "Crimea is Russia" in Simferopol yesterday, Ukraine's interim prime minister declared the Black Sea territory "has been and will be a part of Ukraine."
The escalating conflict sent Ukraine's finances plummeting further, prompting Western leaders to prepare an emergency financial package.
Yanukovych, whose abandonment of closer ties to Europe in favor of a bailout loan from Russia set off three months of protests, finally fled by helicopter last week as his allies deserted him. The humiliating exit was a severe blow to Russian President Vladimir Putin, who had been celebrating his signature Olympics even as Ukraine's drama came to a crisis.
The Russian leader has long dreamed of pulling Ukraine - a country of 46 million people considered the cradle of Russian civilization - closer into Moscow's orbit.