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Russia accused Kiev on Monday of violating a deal backed by the United States and Europe that was intended to keep the peace in eastern Ukraine.

Russian Foreign Minister Sergey Lavrov made the comments after a deadly firefight in the pro-Russian separatist-controlled city of Slaviansk saw at least three people killed Sunday. He said the incident showed that Kiev was not in control of "extremists" in the country.

"Steps are being taken - above all by those who seized power in Kiev - not only that do not fulfill, but that crudely violate the Geneva agreement," Lavrov told a news conference in Moscow, according to a translation by Reuters. "The authorities are doing nothing, not even lifting a finger, to address the causes behind this deep internal crisis in Ukraine."

WATCH: More violence in Ukraine

The U.S. and members of the European Union have been unequivocal in their claim that Russia is behind the stirred tensions in eastern Ukraine, where separatists have occupied several government buildings and are demanding a referendum to join Russia.

A masked protester guards the barricades as the Russian national flag flies at a regional office of the security service in Luhansk, Ukraine, on Monday.Alexander Zemlianichenko / AP

Lavrov added that Russia would not let Ukraine slip into civil war.

"There has been a surge in appeals to Russia for saving them from this outrage. We are being put into an extremely complex position," he said, according to Russia's Interfax news agency. "Those who are deliberately pursuing a civil war, possibly, in an attempt to start a big, serious bloody conflict, are pursuing a criminal policy. And we will not only condemn this policy but will also stop it."

Reuters contributed to this report.

- Alexander Smith