Russian foreign minister Sergei Lavrov has accused Ukraine of violating an agreement reached in Geneva last week aimed at averting a wider conflict.
"Steps are being taken - above all by those who seized power in Kiev - not only that do not fulfil, but that crudely violate the Geneva agreement," he said.
Lavrov also told a news conference that a deadly gunfight early on Sunday near a Ukrainian city controlled by pro-Russian separatists showed Kiev did not want to control "extremists".
Tensions remain high in eastern Ukraine after at least three died in a day of shooting during what was supposed to be an Easter truce.
In an exclusive interview with NBC News, the Ukrainian Prime Minister warns of the dangers of unchecked Russian expansion and aggression.
Russia, the US and the EU say that all sides have agreed to steps to "de-escalate" the crisis in Ukraine at talks in Geneva.