Ukrainian police have given demonstrators five days to leave public buildings they have occupied in protest against a government policy move towards Russia.
Ministers at a European security conference have urged a peaceful end to the confrontation.
Prime Minister Mykola Azarov defended his government's handling of the crisis since he walked away from a trade deal with the European Union.
He clashed with Germany's foreign minister over charges that police had used excessive force against the protesters.
"Nazis, extremists and criminals cannot be, in any way, our partners in 'eurointegration'," the government website quoted Mr Azarov as telling Germany's Guido Westerwelle.
He was referring to protesters who have blockaded the main government offices and occupied other public buildings.
Mr Westerwelle, who is in Kiev for a foreign ministers' meeting of the Organization for Security and Co-operation in Europe (OSCE), expressed concern about police behaviour at the protests last weekend.
"Recent events, in particular the violence against peaceful demonstrators last Saturday in Kiev worry me greatly," said Mr Westerwelle, who visited the main protest centre on Kiev's Independence Square yesterday.
"Ukraine has a responsibility to protect peaceful demonstrators from any kind of intimidation and violence.
"The way Ukraine responds to the pro-European rallies is a yardstick for how seriously Ukraine takes the shared values of the OSCE," he added, echoing comments of other ministers at the meeting.
The crisis has again exposed a tug-of-war in Ukraine, which has oscillated between the EU and its former masters in Moscow since the Orange Revolution nine years ago overturned the post-Soviet political order.
Russian Foreign Minister Sergei Lavrov, however, accused some of his European counterparts of over-reacting to President Viktor Yanukovych's abrupt decision last month to pursue closer trade relations with Russia.
"This situation is linked with the hysteria that some Europeans have raised over Ukraine which, using its sovereign right, decided at the current moment not to sign any agreement which Ukrainian experts and authorities considered isadvantageous," Russia's Itar-Tass news agency quoted Mr Lavrov as saying on the sidelines of the OSCE meeting.
The stand-off between pro-EU protesters and the government, is taking a toll on Ukraine's fragile economy.
The central bank has twice been forced to support the currency this week and the cost of insuring the country's debt against default has risen further.
But Mr Yanukovych, who is visiting Beijing, suggested some relief could be on the way, signing documents for deals with China on agriculture, infrastructure improvement and energy.
"We have not yet calculated what the equivalent in money will be," he was reported as saying by Interfax news agency.
"But earlier we reckoned that we are talking about approximately $8bn of investment into the economy."
China supported Mr Yanukovych's right to decide the direction of trade policy.
"Ukraine, domestically, is in flux," Vice Minister of Foreign Affairs Cheng Guoping told reporters.
"The Chinese government respects Ukraine's internal choice ... the Ukrainian government has the ability to, within the scope of the law safeguard Ukraine's stability in this situation," said Mr Cheng.
Ukraine faces huge problems in financing its current account deficit, with outside funding needs estimated at €12.5bn next year to meet debt repayments and the cost of imported natural gas.
Severely depleted central bank reserves are also putting Ukraine at risk of a balance-of-payments crunch.
The street protests were triggered by Mr Yanukovych's government abruptly announcing on 21 November that it was suspending preparations for signing an association and trade pact with the EU after years of careful negotiations and reviving trade ties instead with Russia.
The Kiev government says it has not walked away from a deal with Europe, but is taking a strategic "pause" while it seeks to negotiate a new "roadmap" with Russia to help it patch up its economy.
Mr Azarov's deputy, Serhiy Arbuzov, who is preparing to head Ukraine's first high-level delegation to Brussels soon to repair some of the political damage, suggested the government might be ready to consider one of the opposition's demands – early parliamentary elections.
But there has been no suggestion from Mr Azarov that he is ready to go along with this idea.
In his comments to Mr Westerwelle, at a face-to-face meeting on the sidelines of the OSCE meeting, he spoke only of not giving in to "extremist" views from the streets.
On the eve of the OSCE meeting, Mr Westerwelle visited Independence Square - focal point of the protest - with two Ukrainian opposition leaders, former economy minister Arseny Yatsenyuk and Vitaly Klitschko, a heavyweight boxing world champion.
About 3,000 demonstrators, evoking memories of the 2004-5 "Orange Revolution", have set up an encampment there, huddling round blazing braziers, swapping anecdotes about the events of the day and following news developments on a huge TV screen.
US Secretary of State John Kerry, in neighbouring Moldova after skipping a visit to Ukraine, said Ukrainians should be free to choose their future.
"This is about building the bridges of opportunity and defining the future of your own hopes and aspirations," he said.
"To the people of Ukraine we say the same thing: 'You too deserve the opportunity to choose your own future'."