Armed separatists took control of a city in eastern Ukraine on Saturday and Kiev prepared troops to tackle what it called an "act of aggression by Russia", pushing the conflict between the neighbors into a dangerous new phase.
Russian Foreign Minister Sergei Lavrov said Ukraine was "demonstrating its inability to take responsibility for the fate of the country" and warned that any use of force against Russian speakers "would undermine the potential for cooperation" including talks due to be held on Thursday among Russia, Ukraine, the United States and the European Union.
The city's mayor said she supported the protesters, and more than a thousand people gathered in front of the police station, chanting: "Moscow, Crimea, Russia!".
They cheered as the Ukrainian flag was replaced with the blue, black and red of the self-declared Donetsk Republic.
"We want to join Russia. We would be very grateful if Russia helps us," said a gunman who gave his name as Alexander, wearing camouflage fatigues and a black balaclava mask.
"We will stand until victory. Honestly, it's not scary for me to die for freedom."