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
Ukrainian president Viktor Yanukovich has claimed protesters are "shooting to kill" as the violence continues to escalate in Kiev.
"They (the protesters) went on to the offensive. They are working in organised groups. They are using firearms, including sniper rifles. They are shooting to kill," a statement from Yanukovich's office read.
Mr Yanukovich said the number of dead and injured among police officers "is dozens."
Earlier, police were pictured carrying sniper rifles with medics for the protesters claiming many of the fatalities have resulted from gunshot wounds.
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.