A Russian-backed separatist leader in eastern Ukraine announced the evacuation of his breakaway region's residents to southeast Russia on Friday after an increase in shelling.

Announcing the move on social media, Denis Pushilin, head of the self-proclaimed Donetsk People's Republic, said Russia had agreed to provide accommodation for people leaving and that women, children and the elderly should be prioritized.

There was no immediate comments from Russian officials or from Kyiv, and a Reuters witness in the region's capital of Donetsk said there were no signs yet of an evacuation.

"As of today, Feb. 18, a mass centralized evacuation of the population to the Russian Federation has been organized," Pushilin said. "Women, children and the elderly are to be evacuated first," he said.

Washington and its allies have raised fears that the upsurge in violence in the region could form part of a Russian pretext to invade Ukraine. Tensions are already high over a Russian military buildup to the north, east and south of Ukraine.

Russia, which denies planning to attack, voiced alarm earlier on Friday over a sharp increase in shelling in the region known as the Donbass.

Several hundred thousand people plan to leave the Donetsk People's Republic to Russia's region of Rostov, the Interfax news agency cited a source in the self-declared republic's parliament as saying.