Up to 1,000 Ukrainian nationalists have rallied in central Kyiv to demand the ouster of the government.
The demonstrators set up six tents on Independence Square on February 21, saying they plan to stay there all night.
On February 20, nationalists threw rocks through the windows at the offices of two Russian banks in Kyiv and ransacked furniture and equipment inside.
Police, which did not intervene, said a criminal case had been opened over the incident.
The attack took place as thousands attended ceremonies marking the second anniversary of protests that brought down Russia-friendly President Viktor Yanukovych Union.
Political tensions have risen in Ukraine in recent weeks amid growing public disenchantment with the pro-Western government over a lack of progress on reforms.
Prime Minister Arseniy Yatsenyuk survived a no-confidence vote in parliament on February 16, after President Petro Poroshenko called on him to resign "in order to restore trust" in the government.