More than one million people have been displaced by the conflict in Ukraine, including 814,000 Ukrainians now in Russia with various forms of status, the UNHCR United Nations refugee agency said on Tuesday.

Numbers displaced inside Ukraine by the fighting have nearly doubled in the past there weeks to at least 260,000 and more are fleeing, it earlier told a Geneva news briefing.

"It's safe to say you have over a million people now displaced as a result of the conflict, internally and externally together," Vincent Cochetel, director of the UNHCR's bureau for Europe, later told reporters. "I mean 260,000 in Ukraine, it's a low estimate, 814,000 in Russia, then you add the rest ... Belarus, Moldova, European Union."

UN refugee chief Antonio Guterres warned of dire consequences if the spiraling crisis in eastern Ukraine, which has killed more than 2,600 people since mid-April, is allowed to continue.

"If this crisis is not quickly stopped, it will have not only devastating humanitarian consequences, but it also has the potential to destabilize the whole region," he said in a statement.

"After the lessons of the Balkans, it is hard to believe a conflict of these proportions could unfold on the European continent," he added.