At least three protesters have been killed in clashes as Ukraine's prime minister takes a hard line against demonstrators flouting anti-protest laws.
Mykola Azarov said on Wednesday that anti-government protests had brought "terrorists" onto the streets of Kiev and pledged to punish all "criminal action", even as protesters confronted police near government headquarters.
"I am officially stating that these are criminals who must answer for their action," Azarov said.
Wednesday's violence came after Ukrainian security forces started dismantling barricades at the protest camp in downtown Kiev, where demonstrators and police have been facing off for the past two nights.
It is reported that two of the victims died from gunshot wounds and were found less than three hours apart in a national library close to the clashes.
The third died in a fall from the top of Dynamo football stadium.
Azarov said opposition leaders should be held responsible for the deaths and said that police at the site of the clashes did not have live ammunition.
The wounds resembled those caused by live ammunition, Oleh Musiy, coordinator of the protesters' medical corps, told the AP news agency.
EU foreign policy chief Catherine Ashton on Wednesday urged "an immediate end" to the escalating violence, while the Polish Foreign Ministry has summoned the Ukrainian ambassador.
Al Jazeera's Nadim Baba, reporting from Kiev, said some protesters had become more determined as a consequence of Wednesday's events.
"It's not clear how news of the deaths will change the nature of these protests, but for now people are continuing to arrive here at the scene of the clashes," our correspondent said.
The violence began when protesters braved heavy snow to remain in Kiev's central square on Wednesday morning, despite warnings from Azarov that security personnel could use force to disperse demonstrations.
Azarov told Russian television that if "provocateurs" did not stop, the authorities could act under controversial new laws that essentially ban large protests in Ukraine.
Azarov added that he hoped there would be no need for the use of force to disperse the protests.
"We are hoping for common sense," he said. "People need to understand that they are being offered chaos and destruction."
On Tuesday, President Viktor Yanukovych refused to meet with an opposition leader, dimming hopes of a peaceful solution to the political crisis.
Russian Foreign Minister Sergei Lavrov warned that the situation in Ukraine was spiralling out of control after two months of protests over Yanukovych's failure to sign a deal with the European Union.
The UN's High Commissioner for Human Rights, Navi Pillay, has called the situation in Ukraine "very worrying" and said the government should suspend the controversial anti-protest laws.