Pro-European Union activists guard the barricades during clashes with riot police in Independence Square on Wednesday. Photo: AP
Ukrainian security forces on Wednesday pulled out of the epicentre of mass protests in Kiev after a nine-hour standoff with thousands of demonstrators, in a major boost for the opposition to President Viktor Yanukovych.
Elite Berkut anti-riot police and interior ministry special forces moved against the protestors who have occupied Kiev's Independence Square for over a week at around 2am.
US Secretary of State John Kerry expressed "disgust" at the crackdown, which came as Assistant Secretary of State Victoria Nuland and EU foreign policy chief Catherine Ashton were in Kiev for talks with all parties to find a way out of the crisis.
Security forces tore down the barricades that protesters angry at Yanukovych's rejection of an EU pact under Russian pressure had erected around Independence Square.
Thousands of armoured police seized control of part of the square by forming a human chain, but the demonstration continued as before over much of the area with thousands of protesters arriving as morning broke.
Protesters finally massed in enough numbers to regain the upper hand, thwarting a bid by security forces to retake Kiev city hall, which has been occupied by some 200 opposition activists for over a week.
Police outside the building used truncheons to beat protesters, who responded with sticks. But activists in the upper storeys of the building doused the police with freezing water from a fire hose, forcing them to leave.
Activists cheered as police left Independence Square, and the opposition set about rebuilding the barricades knocked down earlier.
Ukrainian opposition leader Arseniy Yatsenyuk called for a millions-strong protest in Kiev after the police actions, predicting that the regime of Mr Yanukovych would fall.
"We will not forgive this. Here there will be millions and his regime is going to collapse," Mr Yatsenyuk, the leader of the party of jailed ex-premier Yulia Tymoshenko, told protesters on Independence Square.
"Yanukovych spat in the face of the United States and the EU member states," he said.
World boxing champion and leader of the UDAR (Punch) opposition party Vitali Klitshcko told the protesters: "Kievans rise up! Only together can we win our right to live in a free country."
Police at the scene said their aim was not to disperse the entire protest but to free up Kiev's main Khreshchatyk Street - which passes through the middle of the square - for traffic.
The leader of the nationalist Svoboda (Freedom) movement Oleg Tyagnybok said that several protesters had been injured and the authorities had detained 11 people.
Mr Yanukovych's decision to scrap key trade and political agreements with the EU and police violence against protesters have plunged the ex-Soviet country into its most acute political crisis since the 2004 pro-democracy Orange Revolution.
The police operation came just hours after Mr Yanukovych held talks with Baroness Ashton in Kiev and prompted swift personal condemnation from Mr Kerry.
The US Secretary of State said Washington "expresses its disgust with the decision of Ukrainian authorities to meet the peaceful protest ... with riot police, bulldozers, and batons, rather than with respect for democratic rights and human dignity".
"This response is neither acceptable nor does it befit a democracy," he added.
The EU's delegation in Kiev said it was seeking to contact Ukrainian authorities to prevent the use of violence against citizens.
"The authorities didn't need to act under the cover of night," Baroness Ashton said in a statement.
In a sign of Europe's support for the demonstrators, Baroness Ashton late Tuesday personally visited Independence Square, known locally as the Maidan.
Symbolically, Ms Nuland returned to the Maidan as the security forces were pulling out on Wednesday, handing out bread to both the demonstrators and the security forces.