Demonstrators have refused to move as pro-EU protests on the streets of Kiev enter their second day.
Close to the parliament building in the capital Kiev it is reported some protesters attempted to enter a government building but were forced back by police using batons and tear gas.
The crowd of around a thousand was joined by the leader of the opposition the reigning World Boxing champion Vitali Klitscho.
He called on the demonstrators to maintain pressure on the government after it decided not to sign a major trade deal with the EU.
Violent clashes had erupted on Sunday night when more than 100,000 people gathered in European Square.
The protest was the biggest in Ukraine since the 2004 Orange Revolution.
Pro-EU supporters want Ukraine’s President Viktor Yanukovich to sign the trade pact with the European Union as agreed, during a summit in Lithuania on Friday.
The government has said it cannot afford to break ties with Russia which is trying to bring Kiev into its own customs union.
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