Russia and Ukraine have been locked in a tense stand-off since Russia's upper house of parliament approved the deployment of its forces in Crimea on March 1. Armed men -- without military insignia, but believed to be Russian -- have been guarding airports and government buildings on the Crimean peninsula, while more forces were massing near the Kerch Strait, which separates Crimea from Russia.
Russia's Military Presence in Crimea

1
An armed man stands outside the Cabinet of Ministers building in Simferopol, the regional capital of Crimea.

2
Ukrainian servicemen walk near Simferopol as a military vehicle, believed to be property of the Russian army, follows behind them.

3
A Cossack member of a pro-Russian paramilitary unit stands outside the regional parliament building in Simferopol.

4
Armed men in military uniforms, believed to be Russian soldiers, block access to a Ukrainian naval base near Feodosia, Crimea.