Ukrainian riot police have stormed the main opposition camp in Kiev after clashes left at least 21 people dead and many more wounded in the bloodiest day in three months of protests.
Opposition leader Vitali Klitschko called on women and children to quit the encampment on Kiev's iconic Independence Square as riot police began their assault.
But some 25,000 protesters remained on the square after the expiry of a 6pm ultimatum from security forces demanding calm be restored.
At least 14 protesters and seven policemen were killed during the violence that erupted in Kiev on Tuesday and continued into the early hours of Wednesday.
Many were killed by gunshot and hundreds more injured, with dozens of them in a serious condition, police and opposition representatives said.
Protesters seized back control of Kiev's city hall, with about 30 activists setting up a first aid point inside the building, which the opposition had left on Sunday as part of an amnesty deal with the authorities, according to AFP reporters on the scene.
However, the standoff in Independence Square was continuing.
The European Union, United Nations, United States and NATO all voiced concern over the clashes, AFP reports.
EU foreign policy chief Catherine Ashton says she is "deeply worried about the grave new escalation".
UN chief Ban Ki-moon is calling for restraint and dialogue while Washington says it is "appalled" by the violence, warning Ukraine's President Viktor Yanukovych must "de-escalate the situation".
NATO head Anders Fogh Rasmussen says he is "seriously concerned", urging "all parties to refrain from violence and to urgently resume dialogue, including through the parliamentary process".
The clashes were the first violent ones since mid-January in the Ukrainian capital, which has been wracked by anti-government demonstrations since President Yanukovych in November rejected an EU pact in favour of closer ties with historical master Russia.