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 has requested support from the International Monetary Fund, its Managing Director Christine Lagarde has confirmed.
Lagarde said the IMF is discussing with international partners how best to help Ukraine, and will send a team to Kiev in the coming days.
Ukrainian finance minister Oleksander Shlapak said they are asking for at least $15 billion.
"Today we requested the IMF send a mission and we hope that it will be here next week," the minister was quoted as saying by Interfax news agency.
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.