The pro-Russia separatist leader in Donetsk claimed that the Russian invasion will be over soon.

"The liberation movement will be over pretty quickly," the leader of the self-proclaimed Donetsk People's Republic said hours after Russia's invasion.

"I can say this will end soon," said Denis Pushilin, noting that the military venture is in full force and that all cities and villages in the region will be freed soon.

Early Thursday, explosions were reported in several Ukrainian provinces, including the capital Kyiv, and tanks reportedly crossed the border from Belarus into Ukraine.

The news followed Russian President Vladimir Putin announcing a military intervention in Ukraine, just days after recognizing two separatist-held enclaves in eastern Ukraine. The recognition of Donetsk and Luhansk drew international condemnation and threats of tougher sanctions against Moscow.

Russia has amassed over 100,000 troops around Ukraine in recent months, but Putin repeatedly denied any intention of invading.