Embattled Ukrainian President Viktor Yanukovich has told opposition leaders they have "crossed the limits", after a night of violence in the capital Kiev left at least 26 people dead, including 10 policemen, and many more injured, according to the health ministry.
In a letter published on his website on Wednesday, Yanukovich accused opposition leaders of ignoring "the basic principle of democracy".
He said: "They crossed the limits when they called people to arms. And it is a blatant violation of the law. I have some advisers who try to persuade me to the use of force. But I always thought the use of force as a wrong approach."
The European Union's foreign policy spokesman Catherine Ashton has convened an extraordinary meeting of EU foreign ministers on Thursday.
European Commission President Jose Manuel Barroso said on Wednesday: "We have ... made it clear that the EU will respond to any deterioration on the ground. We therefore expect that targeted measures against those responsible for violence and use of excessive force can be agreed by our member states as a matter of urgency."
Protesters continued to clash with riot police on Kiev's Independence Square on Wednesday. At least 241 have been injured, reported AP news agency.
Clashes with riot police started in Kiev early on Tuesday morning, after thousands of protesters marched towards parliament, where opposition leaders accused pro-government factions of dragging their feet on a constitutional reform that would limit presidential powers - a key opposition demand.
The confrontation grew deadly as police stormed barricades set up by anti-government protesters at the capital's Independence Square, where they were met by Molotov cocktails.
Yanukovich said that people who broke the law must go to court, which would determine their punishment.
"Therefore, I once again urge the leaders of the opposition, who argue that they too seek a peaceful settlement immediately disassociate themselves from the radical forces that provoke bloodshed and clashes with law enforcement. Or admit that they support the radicals. Then it will be another story."
Unrest broke out in Ukraine last year when Yanukovich rejected a free-trade agreement with the European Union and opted for a $15bn package of Russian credits and cheaper gas to support Ukraine's ailing economy in November.
'Grave new escalation'
As reports emerged of protesters taking over government buildings in other Ukrainian cities, a meeting at the presidential residence between Yanukovich and opposition leaders Vitaly Klitschko and Arseny Yatsenuk broke down, according to opposition sources.
|Police crack down on Ukraine's Maidan movement
Klitschko said in a statement that Yanukovich's reaction to the situation was "inadequate".
The Russian Foreign Ministry said that Tuesday's violence was a "direct result of connivance by Western politicians and European structures that have shut their eyes ... on the aggressive actions of radical forces".
It said that the opposition's actions are being viewed by Moscow as an attempted coup.
Denouncing the "grave new escalation" in Kiev, EU foreign policy chief Catherine Ashton condemned "all use of violence, including against public or party buildings".
"I urge the leadership of Ukraine to address the root causes of the crisis," she said, calling for an urgent return to a parliamentary process.
Echoing Ashton's sentiments, a number of Western countries, including the US and France, called for an end to the violence in Kiev and restraint by security forces.
UN Human Rights chief Navi Pillay has condemned the violence and urged all sides to show restraint. She called for an independent investigation to ensure accountability for the deadly clashes.