Riot police in the Ukraine advanced onto a central Kiev square occupied by protesters, after at least 14 people died in the worst day of violence since demonstrations erupted against President Viktor Yanukovich 12 weeks ago, Reuters reports.
Protesters on Independence Square responded with petrol bombs, fireworks and stones, as police moved slowly forward, hours after the state security service had set a deadline for the demonstrators to end disorder or face "tough measures."
Live television footage showed the police throwing stun grenades at the protesters separated from them by a line of burning tents, tires and wood.
Western powers warned Yanukovich against trying to smash the demonstrations and opposition leader Vitaly Klitschko, fearing an assault, urged women and children to leave the central square.
A police spokeswoman quoted by Reuters said seven civilians and six policemen died in several hours of clashes, some from gunshot wounds, in what was also Ukraine's bloodiest day since it gained independence from the Soviet Union in 1991. A representative of the protesters said one other civilian had also died.
Nationwide protests against Yanukovich erupted in November after he bowed to Russian pressure and pulled out of a planned far-reaching trade agreement with the European Union.
The United States and its Western allies are urging Yanukovich to turn back to Europe and the prospect of an IMF-supported economic recovery, while Russia accuses them of meddling.
In Washington, White House spokesman Jay Carney said the United States was appalled by the violence and urged Yanukovich to restart a dialogue with opposition leaders. "Force will not resolve the crisis," Carney told a briefing, according to Reuters.
Earlier on Tuesday, clashes raged for several hours outside the parliament building, where opposition lawmaker Lesya Orobets said three demonstrators were killed and taken to a nearby officers' club used as a medical center. More than 100 people were injured, she said.
EU foreign policy chief Catherine Ashton, who has tried to broker a power-sharing transition, urged Ukraine's leadership "to address the root causes of the crisis."