Russian President Vladimir Putin has said Moscow was "thinking" of making it easier for all Ukrainians to obtain Russian citizenship after the Kremlin moved to grant passports in the country's separatist east, causing uproar in Kiev. 

"We are actually thinking about providing citizenship in a simplified order to all citizens of Ukraine, not only residents of the Lugansk and Donetsk republics," Russian president told the press during his visit to Beijing, referring to the unrecognised separatist republics governed by Moscow-backed rebels.

This week Vladimir Putin signed a decree allowing people living in the breakaway regions to receive a Russian passport within three months of applying for one.

The conflict between the Ukrainian government and breakaway rebels began after Moscow annexed Kiev's Crimea peninsula in 2014. The war has claimed some 13,000 lives.

The declaration sparked more condemnation in Kiev.

"Russia wants further escalation and chaos in Ukraine and therefore continues to complicate the rules of the game," Dmytro Kuleba, Kiev's permanent representative to the Council of Europe, wrote on Twitter. 

The move came just days after Ukraine elected comedian Volodymyr Zelensky as president. The actor, due to be inaugurated by early June, called for more international sanctions against Russia in response.

The European Union also condemned the move, calling it a fresh assault on Ukraine's sovereignty.

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President Putin said he wanted to "understand" Zelensky's position on the conflict.

He did not exclude talks with the comedian - a political novice - with whom he said he was ready to "have a discussion." 

The Russian leader said "everyone is tired of this conflict" and that Ukraine expects solutions on the war from the country's new leadership.

He also said Moscow will fulfil all "social responsibilities to our new citizens of Russia."

After they receive a Russian passport, residents of eastern Ukraine will be eligible for "social payments, pensions and their increase, everything will be fulfilled."

Such payments would not strain the Russian budget, he claimed, saying that the decision had been "calculated".