Ukrainian opposition leaders have called for new mass protests against President Viktor Yanukovich's refusal to sign a trade deal with the European Union.
They are demanding new elections, and the impeachment of the president.
A former minister said the political opposition was setting up a national resistance headquarters and preparing to call a nationwide strike.
A giant rally was called for Sunday and opposition members say the size of the crowd will help them decide what their next move will be.
Thousands of anti-government demonstrators regrouped in Mykhayllivska Square in Kiev on Saturday after police used batons to disperse protesters gathered in the city's Independence Square.
The BBC reports dozens of people were hurt when police forcibly broke up the crowd of about 400 in the early hours of Saturday morning. Protest organiser Sergei Milnichenko said officers had used tear gas.
Mr Yanukovych said he was outraged at police officers who used truncheons to beat some of the protesters early on Saturday, and Ukraine's Prime Minister, Mykola Azarov, has promised an investigation.
Jailed ex-prime minister Yulia Tymoshenko has urged people to overthrow the government following Mr Yanukovich's rejection of an EU partnership deal.
Ukraine refused to sign the deal after apparent pressure from Russia.
At the end of a summit in the Lithuanian capital on Friday, EU leaders warned they would not tolerate Russian interference in the bloc's relations with former Soviet republics.
The summit reached provisional accords with Georgia and Moldova.