A masked man, believed to be a Russian soldier, holds a Crimean flag as members of a pro-Russian self-defense unit stand in formation Monday in the regional capital of Simferopol. Vasily Fedosenko /Reuters /Landov hide caption

itoggle caption Vasily Fedosenko /Reuters /Landov

A soldier in an unmarked uniform, but believed to be from the Russian army, stands outside one of the Ukrainian military bases in Crimea that have been surrounded by Russian forces. Ukrainian guards look on from inside the base. David Mdzinarishvili/Reuters/Landov hide caption

itoggle caption David Mdzinarishvili/Reuters/Landov

Viktor Yanukovych, who says he's still the president of Ukraine, at his news conference Friday in the southern Russian city of Rostov-on-Don. Yuri Kochetkov /EPA /LANDOV hide caption

itoggle caption Yuri Kochetkov /EPA /LANDOV

On Friday, armed men took control of the international airport in the city of Simferopol, on the Crimean peninsula. Gunmen took control of another airport in Crimea, as well. David Mdzinarishvili/Reuters/Landov hide caption

itoggle caption David Mdzinarishvili/Reuters/Landov

Flags fly outside the Crimean parliament building in Simferopol on Thursday during a rally by pro-Russian protesters. Gunmen seized government buildings in the city. David Mdzinarishvili /Reuters/Landov hide caption

itoggle caption David Mdzinarishvili /Reuters/Landov

Praying For Those Who Died: Mourners were in Kiev's Independence Square again on Tuesday. It was the site of protests in recent months, and was where more than 80 people died last week in violence blamed on security forces. Louisa Gouliamaki /AFP/Getty Images hide caption

itoggle caption Louisa Gouliamaki /AFP/Getty Images

People pass by a portrait of prominent opposition leader Yulia Tymoshenko at Independence Square in Kiev, Ukraine, on Monday. Tymoshenko, a former prime minister, is one of the leaders who have emerged after the ouster of President Viktor Yanukovych, but she is also a controversial figure. Marko Drobnjakovic/AP hide caption

itoggle caption Marko Drobnjakovic/AP

In Kiev last month, this anti-government protester in protective gear stood in front of a poster featuring an image of former Prime Minister Yulia Tymoshenko. Her jailing on what supporters believe were bogus charges was among the complaints protesters raised. Darko Bandic/AP hide caption

itoggle caption Darko Bandic/AP

Ukrainian President Viktor Yanukovych (right) and opposition leader Vitali Klitschko shake hands Friday after signing an agreement that diplomats hope will end the bloodshed in Kiev. Tim Brakemeier/EPA/Landov hide caption

itoggle caption Tim Brakemeier/EPA/Landov

Anti-government protesters wave flags and shout slogans Tuesday in Kiev, Ukraine. Vasily Fedosenko /Reuters/Landov hide caption

itoggle caption Vasily Fedosenko /Reuters/Landov