Ukraine's acting president has warned Russia that troop movements outside its naval base in Crimea would be seen as an "act of aggression". Armed men seized regional government headquarters and parliament and the Russian flag is flying from buildings
Ukraine's capital Kiev erupted into a full-scale battle today leaving at least 39 people dead, with many of those killed victims of pro-Government snipers.
As fighting continued - which left many people injured on both sides - a group of 67 police officers were taken hostage by demonstrators.
Europe Editor James Mates reports from Kiev:
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.