Ukrainian protesters stood their ground today after an overnight sweep by riot police.
Their leaders dismissed an offer of talks from a president they say must quit for favouring ties with Russia over the European Union.
Pressed by Europe and the United States, which condemned the destruction of a protest camp in central Kiev, President Viktor Yanukovych offered to meet opposition leaders to find a way out of a crisis that began last month when he yielded to pressure from Russia and spurned a free-trade deal with the EU.
But his opponents, whose supporters continue to occupy the capital's City Hall, rejected his invitation and stuck to demands that the president and his government resign.
The authorities had made their most forceful attempt so far to reclaim the streets, sending in battalions of riot police with bulldozers to clear Independence Square.
There were scuffles and arrests but police did not enter the nearby City Hall and by morning they withdrew from the streets.
Within hours, after meetings with US and European Union officials who had urged him to compromise, Mr Yanukovych asked his opponents to meet him to negotiate a way out of the impasse.
He said: "I invite representatives of all political parties, priests, representatives of civil society to national talks," he said in a statement that also called on the opposition not to "go down the road of confrontation and ultimatums".
One protest leader, Oleh Tyahnibok, dismissed the move as "a farce and a comedy", while Arseny Yatsenyuk, a leader of a major opposition party, said there should only be talks once their demands had been met.
These include the resignation of the president and government and a release of prisoners.
In some of the strongest comments from the US so far, a White House spokesman urged Mr Yanukovych to listen to the people and resume Ukraine's integration with Europe.
"Violence of this sort that we have seen on the streets of Kiev is impermissible in a democratic state," he added.
US Secretary of State John Kerry spoke of "disgust" at the use of force and a spokeswoman for his department said the US was considering sanctions against Ukraine, among other options.
Such a move could further sour relations with Russia, which says the west is trying to intimidate Ukraine to weaken Russia.
At stake is the future of a country of 46 million people, torn between popular hopes of joining the European mainstream and the demands of former Soviet master Russia, which controls the flow of cheap natural gas needed to stave off bankruptcy.
At the main protest camp on Independence Square, pop stars, politicians and priests had pleaded with police not to shed blood.
The interior minister called for calm and promised that the square would not be stormed.
But even after the police left the streets, Vitaly Klitschko, a world boxing champion who has emerged as one of the main figures of the opposition, said the overnight action had "closed off the path to compromise".
"We understand that Yanukovych has not wish to talk to the people and only understands physical force," he said.
The interior ministry appealed for restraint, however, and the police action stalled after day broke, with temperatures in the snowbound city stuck well below freezing.
Some riot police left to cheers from lines of protesters.
At City Hall, demonstrators had sprayed police with water from a hose and had lobbed a Molotov cocktail from a window into a police truck before the officers finally withdrew.
On the square, protesters, many wearing hardhats in orange, the colour that symbolised a successful popular revolt against a fraudulent election in 2004, had listened to prayers and a plea from national pop icon Ruslana: "Do not hurt us!"
Some protesters held mobile phones in the air like candles and sang the national anthem, while church bells rang out from a cathedral a kilometre away, as in times of danger centuries ago.
"He is spitting in the faces of the United States, 28 countries of Europe, 46 million Ukrainians," opposition leader Yatsenyuk said of Mr Yanukovich during the night.
"We will not forgive him this."
The eventual police withdrawal was greeted with euphoria.