Pro-Russian separatists scuffled with pro-government supporters in eastern Ukraine Sunday, even as a deadline loomed for the separatists to lay down their arms.
Ukraine's acting president, Oleksandr Turchynov, has given pro-Russian protestors who occupy state buildings in the east of the country until Monday morning to disarm, or face a "full-scale anti-terrorist operation".
In a televised speech Sunday, Mr. Turchynov vowed Kyiv will not let Russia take over eastern Ukraine after its annexation of the Crimean peninsula last month. He accused Moscow of carrying out a war against Ukraine, once a part of its Soviet empire.
The Russian foreign ministry immediately branded Ukraine's operation "a criminal order."
Mr. Turchynov's speech came hours after Ukrainian special forces and pro-Russian militia exchanged gunfire in the eastern Ukrainian city of Slovyansk, with both sides reporting casualties. One day earlier, pro-Russian gunmen took over the Slovyansk police station, and government facilities in the largely ethnic Russian cities of Donetsk and Kramatorsk.
The U.S. ambassador to the U.N., Samantha Power, told ABC's This Week the unrest in eastern Ukraine "bears the tell-tale signs of Moscow's involvement."
NATO chief Anders Fogh Rasmussen said he is "extremely concerned" about what he described as a "concerted campaign of violence by pro-Russian separatists" seeking to destabilize Ukraine. He called on Russia to "de-escalate the crisis" and pull back thousands of troops from near the Ukrainian border.
Top diplomats from Russia, the United States, Ukraine and the European Union are set to hold emergency talks on the crisis April 17 in Geneva. White House officials say U.S. Vice President Joe Biden will travel to Kyiv April 22.