MOSCOW, April 16 -- The escalation of the conflict in Ukraine has brought the country to the verge of civil war, Russian President Vladimir Putin has said.

Putin warned of the possibility during a late night telephone conversation with German Chancellor Angela Merkel on Tuesday, the Kremlin press service said Wednesday.

The two leaders "exchanged opinions about the anti-constitutional course of the incumbent Kiev authorities towards the suppression by force of popular protests in southeastern Ukraine," according to the press service.

Putin and Merkel accentuated the importance of the four-party negotiations between Russia, the European Union, the United States and Ukraine scheduled for Thursday, expressing the hope that the Geneva meeting could send a "strong message" to encourage events to take a peaceful route, it added.

Meanwhile, Putin highlighted the importance of solving the problems of the Ukrainian economic stabilization and the provision of deliveries and transit of Russian natural gas to Europe, said the Kremlin.

A new wave of unrest erupted in eastern Ukraine over the weekend, as pro-Russia activists seized several government buildings in the cities of Donetsk, Lugansk and Kharkov, demanding a referendum on autonomy and closer ties with Russia.

Ukraine accused Russia of being behind the unrest, but Moscow has firmly denied involvement in Ukraine's domestic affairs.

Russian Foreign Minister Sergei Lavrov on Monday said Russia does not interfere in Ukraine's internal affairs, which would contradict their interests.