Ukraine's acting president has appealed for calm after the seizure of buildings on the country's Crimea peninsula by "criminals in military fatigues".
Oleksandr Turchynov said he has given orders for security structures to take "all measures" needed to protect Ukraine's citizens.
Ukraine's interim President has expressed concerns about signs of separatism as opposition in Russian-speaking regions grows.
Hundreds of Ukrainians and journalists flocked to the presidential palace, as reports emerged that President Yanukovich had left the city.
Vitali Klitschko was met with boos from anti-government protesters, as he attempted to convince them a peace deal is best course of action.