On Thursday, dozens of masked gunmen believed to militant Russian nationalists seized several government buildings, including the regional parliament building, in Simferopol, the capital of Ukraine's Crimea region, and raised the Russian flag. Meanwhile, across the border, more than 150,000 Russian troops performed readiness tests as Russian fighter jets patrolled the Ukrainian border for the second straight day.

Tensions in Crimea have risen since last week's ousting of President Viktor Yanukovych, whose strong pro-Russia policies were popular in region. Many pro-Russian groups around Crimea have called for protection from Moscow.

The interim government in Kiev is asking Russia not to intervene, though Russia so far has refused to recognized the new government.

"We ask our Russian partners to provide to stick to their... obligations, we believe Russia would never intervene into Ukrainian domestic affairs and will refrain from any steps that would split Ukraine," Prime Minister designate Arseniy Yatsenyuk told the BBC.

Police officers quickly surrounded the seized buildings in Simferopol but remain unsure who's behind the attacks.

Ukraine's acting interior minister wrote on Facebook that measures were "being taken to counter the extremist actions and prevent an escalation of an armed conflict in the center of the city."

"Provocateurs are on the march," Mr. Avakov added. "It's a time for cool heads, the healthy consolidation of forces, and careful action."

Meanwhile, Russia performed a second day of military exercises along the Ukrainian border. "Constant air patrols are being carried out by fighter jets in the border regions," Russia's defense ministry told Interfax.

President Putin has also ordered "snap drills" to test the readiness of about 150,000 troops near the border.

And ousted President Yanukovych has reportedly fled to Russia, where he's seeking to "secure [his] personal safety from the actions of extremists," according to his first statement since losing power last week. From the New York Times:

Mr. Yanukovych, in a written letter published by news agencies here, went on to suggest that largely Russian regions of Ukraine – including the east and Crimea – did not accept "the anarchy and outright lawlessness" that had gripped the country and said that orders by the new authorities to use the armed forces to impose order were unlawful. He clearly meant the response to pro-Russia demonstrations in Crimea, which took an ugly turn on Thursday morning when armed gunmen seized control of the regional Parliament in Simferopol.

"I, as the actual president, have not allowed the armed forces of Ukraine to interfere in the ongoing internal political events," he said, contradicting early reports that he had ordered the military to intervene in Kiev, only to have his order rebuffed. "I continue to order this. In the case that anyone begins to give a similar order to the armed forces and power structures, those orders will be unlawful and criminal."

[Image via AP]