Russia came under heavy criticism from world powers at an emergency meeting of the United Nations Security Council Sunday, as deadly clashes flared between pro-Russian separatists and pro-government supporters in eastern Ukraine.
U.S. Ambassador Samantha Power and British Ambassador Mark Lyall Grant accused Russia of orchestrating the violence.
Power said the instability in Ukraine was "completely man made" She said it was "written and choreographed" by Russia. Grant called on the Security Council to warn Russia against "further military escalation."
Russia, which called the meeting, rejected the charges. Russian Ambassador Vitaly Churkin called on the Council to ask Kyiv to "stop the use of force against eastern Ukrainian people," who are largely ethnic Russians.
The U.N. meeting came ahead of a deadline for the pro-Russian militias in Ukraine to lay down their arms.
Ukraine's acting president, Oleksandr Turchynov, has given pro-Russian protesters 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.
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.