Western diplomats have urged Ukrainian authorities to respect the massive protests gripping the country against the government's decision to freeze ties with the EU and turn to Moscow instead.
Several thousand activists kept up the demonstrations at a central square in Kiev, the capital, and besieged government meetings as the Organisation for Security and Co-operation (OSCE) in Europe's ministerial council began its meeting on the other side of the river.
The meeting had been scheduled long before the protests that have been dominating the country.
US under-secretary of state Victoria Nuland challenged Ukrainian authorities to meet the protests constructively.
"This is Ukraine's moment to meet the aspirations of its people or disappoint them," she told the OSCE meeting. "Democratic norms and the rule of law must be upheld."
Prime Minister Mykola Azarov tried to put a positive spin on the tense situation, saying the protests "are a completely normal development in a country where democracy is developing".
"We will do everything we can to ensure this is a peaceful protest," Mr Azarov said.
With President Viktor Yanukovych away in China, the government showed no sign of yielding to the protests. Police have promised not to use force, but law enforcement bodies were detaining and investigating scores of opposition activists.
Mr Azarov has also warned several pro-EU cities in Ukraine which have gone on strike that the central government in Kiev might cut off funding to them.
The demonstrations were sparked by Mr Yanukovych's decision to ditch a significant treaty with the 28-nation European Union after strong pressure from Russia. They were also galvanised by the violent break-up of a small, peaceful rally by riot police last month.
The protesters are demanding that the government resign and that early elections be called.
Mr Azarov chided the demonstrators, who have occupied or blocked government buildings, saying they are contradicting the values that they claim to support.
"That is not the European way forward," Mr Azarov said of the building occupations.
He also said Ukraine remains committed to moving forward with the EU association and characterised Mr Yanukovych's shelving of the signing as only a pause.
"The time-out we have taken is clearly taken only because of economic difficulties," he said.
Ukraine said it cannot absorb the trade losses with Russia it would have been likely to suffer if it had signed the EU agreement last month.
Meanwhile, Russian foreign minister Sergey Lavrov, speaking at the conference, notably did not mention the Ukrainian protests, which have had a strong anti-Russian element.
Russian President Vladimir Putin's government is determined to bring Ukraine, a former Soviet republic, back into its area of influence.
Later, Europe's top human rights body said that Ukraine's government and opposition leaders seeking its downfall have accepted a proposal to create a panel to investigate the past week's violence against protesters.
Council of Europe spokesman Daniel Holtgen said the panel would include one member each, nominated by the government and the opposition, and that the council would nominate a third member who has substantial human rights credentials.
The violent dispersal of protesters by police on Saturday and Sunday exacerbated opposition anger that was already high over President Yanukovych's shelving of an agreement to establish closer economic ties with the European Union.