Photos: With Ukraine in Disarray, Crimea Heats Up

As unrest continues in Ukraine, pro-Russian forces cause further turmoil in Crimea at the southern tip of the country.

Armed men patrol outside Simferopol International Airport on February 28, 2014.

Armed, masked men in unmarked military uniforms patrol outside Simferopol International Airport in Crimea. Another confrontation is under way at Sevastopol International Airport.

Ukraine's fledgling leadership has called the airport occupations by forces affiliated with Russia an invasion. Meanwhile, former president of Ukraine Viktor Yanukovych has reappeared in Russia after a week on the run.

Ukraine's interior minister called the airport seizures "a direct provocation," but there has been no violence so far. Russia's Black Sea Fleet, based on the Crimean Peninsula, has denied involvement. (Related: "After Ukraine Crisis, Why Crimea Matters")

In Kiev, Oleksandr Turchynov, Ukraine's acting president, convened a meeting of the country's National Security and Defense Council. The parliament has urged Russia to "stop moves that show signs of undermining national sovereignty" in Ukraine and, Reuters reported, asked the United States and Britain to step in. The parliament also called on the United Nations Security Council to debate the issue. (Photos: "Ukraine's Ring of Fire")

The armed men in the Crimean capital of Simferopol surrounded an administrative building but did not enter the airport, where flights were arriving and departing on schedule.

The developments come a day after pro-Russian forces took control of government buildings in Simferopol, where crowds chanted "Russia, Russia" and legislators called for a vote to redefine relations with Ukraine.

Since the collapse of the Soviet Union in 1991, outbursts of pro-Russia fervor have erupted sporadically in Crimea, an autonomous region. The events Thursday, coupled with those in Ukraine, challenge the country's territorial integrity and the geopolitical balance between Russia and the West. (Related: "Behind the Headlines: History and Geography Help Explain Ukraine Crisis")

Gunmen in camouflage seize control of the airport in Simferopol, Crimea's capital.

Russian troops block the road to the military airport in Sevastopol, the port where Russia's Black Sea Fleet is based. Russia has denied involvement in the seizure of two Crimean airports by masked gunmen.

Activist guards monitor a rally outside the Ukrainian parliament building in Kiev's central Independence Square. On Thursday the parliament approved the nomination as prime minister of Arnseniy Yatsenyuk, a prominent leader in the anti-government protests that led to deadly clashes and ended in the ouster of Viktor Yanukovych as president earlier this month. (See photos: "Ukraine's People Power in Photos")

A protesters' camp covers much of Independence Square in central Kiev. Today, Ukraine accused Russia of staging an "armed invasion" of Crimea, where gunmen in unmarked military uniforms seized control of two airports.

Ukrainian lawmakers applaud new Prime Minister Arneniy Yatsenyuk during a session of parliament in Kiev. The 39-year-old Yatsenyuk—a former economy minister, foreign minister, and parliamentary speaker—will try to stabilize the politically divided, financially shaky country.

Russian sailors stand in a line at a naval base in Sevastopol, Crimea, where Russia's Black Sea Fleet is based. Ukraine's new government urged Russia not to abuse its naval rights in Crimea after armed men there seized control of regional government headquarters and parliament and raised the Russian flag.

Viktor Yanukovych speaks at a news conference in Rostov-on-Don, a Russian city some 600 miles (966 kilometers) south of Moscow. It was the first appearance in five days for Yanukovych, the deposed president of Ukraine.

Cossacks attend a pro-Russia rally in Simferopol, the Crimean capital. Armed men in unmarked military uniforms have seized control of two airports in the autonomous region, escalating tensions between Moscow and the West. Russian forces have denied involvement.

A woman holds flowers near a makeshift memorial in Kiev's central Independence Square. The site has been at the center of political upheaval and deadly strife over the past three weeks.

Two priests in Kiev's Independence Square pray at a memorial for people killed in this month's clashes.