Police in the Ukrainian capital Kiev have launched a fresh attack on anti-government protesters as the death toll in renewed clashes has climbed to 25.
The new attempt to uproot the protest stronghold came as President Yanukovych blamed opposition leaders for the worst violence in months of unrest.
After failed overnight talks, he urged them to distance themselves from radical forces.
Activists say the violence has been stoked by the authorities.
Police launched their latest assault on Independence Square, also known as the Maidan, shortly after 04:00 local time (02:00 GMT). Several tents were set ablaze, and water cannon was later used.
A BBC correspondent said police had taken control of a corner of the square for the first time since December.
The protests began in late November, when President Viktor Yanukovych rejected a landmark association and trade deal with the EU in favour of closer ties with Russia.
Tensions had begun to subside as recently as Monday, as protesters ended their occupation of government buildings in return for an amnesty against prosecution.
But violence erupted outside parliament on Tuesday morning as government supporters blocked opposition attempts to scale back the president’s constitutional powers. Correspondents say it was unclear what sparked the clashes, with each side blaming the other.
Fighting spread to surrounding streets and police launched a first attack on Independence Square on Tuesday evening.
In a statement, the health ministry said on Wednesday the number of dead on both sides had risen to 25. Nine of those killed were police, the interior ministry says. A journalist has also died.
Hundreds of people have been treated in hospital for injuries and there are fears the number of deaths could rise still further.
As police gained ground in the Maidan, stones and petrol bombs were met with tear gas.
The protesters tried to hold their defence lines, burning tyres on the barricades and more anti-government activists were said to be on their way to join the camp.
A trade union building where many protesters had been sheltering was set alight and people could be seen climbing down the walls to escape the flames.
There were reports of unrest breaking out elsewhere in Ukraine, including the western cities of Lviv, Ivano-Frankivsk and Ternopil.
‘Island of freedom’
Opposition leaders Vitaly Klitschko and Arseniy Yatsenyuk met President Viktor Yanukovych for late night talks but failed to come to an agreement.
In a statement broadcast on TV news channels on Wednesday morning, President Yanukovych said: “The opposition leaders have disregarded the principle of democracy according to which one obtains power not on the streets or maidans – but through elections.”
“They have crossed the line by calling for people to take up arms,” he said, warning that those responsible for violence would face the law.
But the president added that there was a “better and more effective way” to solve the crisis – through dialogue and compromise.
“It is not too late to stop the conflict,” he said.
Security forces had given the protesters a deadline of 18:00 on Tuesday (16:00 GMT) to leave the square, the scene of a mostly peaceful protest camp since November.
When the deadline expired, riot police advanced with an armoured vehicle, dismantling barricades and firing stun grenades and water cannon.
Protesters have been resisting, throwing missiles from behind piles of burning tyres.
In speeches from the main stage through the night, protest leaders urged people already on the Maidan to stand firm, and called on Ukrainians elsewhere to come to the square.
“This is an island of freedom and we will defend it,” said Vitaly Klitschko, the leader of the Udar (Punch) party.
Mr Yatsenyuk, who heads the Fatherland party, appealed to President Yanukovych to “stop the bloodshed and call a truce”.
He had earlier accused the president of blocking attempts to reform the constitution in parliament.
But MPs who support the president said the proposals had not been thoroughly discussed, and that more time was needed.
There has been widespread international alarm at the bloodshed in Kiev.
- UN Secretary-General Ban Ki-moon has appealed for restraint and “immediate renewal of genuine dialogue”
- EU foreign policy chief Catherine Ashton urged Ukraine’s leaders to address the “root causes of the crisis”
- Russia’s foreign ministry blamed the clashes on the “conniving politics of Western politicians and European bodies”