Ukraine suffered its bloodiest day since Soviet times on Thursday as battles erupted in central Kyiv between riot police and anti-government protesters. Local officials said 39 people were killed, bringing the three-day toll to at least 69 fatalities.
However, medical officials working with protesters said 70 to 100 people died on Thursday alone, some by government sniper fire. Hundreds of others were reported wounded.
Elsewhere, television footage from the western city of Lviv showed scenes of chaos, as anti-government protesters firebombed government buildings and some police declined to intervene.
The White House said Thursday it was "outraged by the images of Ukrainian security forces firing automatic weapons on their own people." The U.S. statement called on President Viktor Yanukovych "to immediately withdraw his security forces from downtown Kyiv and to respect the right of peaceful protest." It also urged protesters to "express themselves peacefully" and pressed the Ukrainian military "not to get involved in a conflict that can and should be resolved by political means."
In Brussels, European Union foreign ministers agreed in emergency session Thursday to impose sanctions on Ukrainian officials deemed responsible for orchestrating the violence in the capital. The measures would include visa bans, asset freezes and restrictions on the export of anti-riot gear to the Ukrainian government. Washington imposed similar sanctions Wednesday.
Three EU foreign ministers (France's Laurent Fabius, Germany's Frank-Walter Steinmeier and Poland's Rodoslaw Sikorski) are in Kyiv, where they met with President Yanukovych to discuss the crisis.
Mr. Yanukovych and the leaders of anti-government protests had agreed on a truce Wednesday, saying it was aimed at "ending the bloodshed and stabilizing the situation...in the interests of social peace." The truce dissolved within hours.
Ahead of the truce announcement, the president fired his army chief, and Ukraine's military declared a nationwide crackdown on what it called "extremist groups." Mr. Yanukovych offered no explanation for the dismissal.
In announcing the "anti-terrorist" operation, the Interior Ministry said protesters elsewhere in the country had overrun government arms depots and seized weapons and munitions. Authorities said they feared those stockpiles were destined for the capital for use by protesters.
In Moscow Thursday, the Kremlin said President Vladimir Putin was sending his top human rights envoy to Ukraine to mediate talks between President Yanukovych and the opposition. The Kremlin - which has condemned the Ukraine protests as a "coup attempt," said the step was taken at the Ukrainian president's request.
Russian-leaning President Yanukovych and the pro-Western protesters seeking to drive him from power are locked in fierce struggle for the future of the country. Local and Western news reports describe scenes this week of open rebellion against the central government in western Ukraine, where data shows most of the population favoring closer ties with the West.
However, the same data, extracted from a national survey in December, shows 36 percent of the nation's 46 million residents -- most of them in Russian-speaking eastern Ukraine -- favor closer ties with Moscow.
Anti-government protests erupted in November, after after Mr. Yanukovych backed away from a trade deal with the European Union in favor of closer ties with Russia.