The crackdown by the authorities came hours after a three-and-a-half-hour meeting between Mr. Yanukovich and Catherine Ashton, the European Union’s foreign policy chief.
The diplomatic consequences became apparent almost immediately. “I was among you,” Ms. Ashton said in a statement on Wednesday morning. “The authorities did not need to act under the cover of night.”
And in unusually strong language, Secretary of State John Kerry expressed the United States’ “disgust” with the authorities’ decision to use force. “This response is neither acceptable nor does it befit a democracy,” he said in a statement.
He added: “As church bells ring tonight amidst the smoke in the streets of Kiev, the United States stands with the people of Ukraine. They deserve better.”
Western leaders, including Vice President Joseph R. Biden Jr., who spoke by telephone with Mr. Yanukovich on Monday, had sternly warned the government against the use of force on peaceful protests. Earlier, on Tuesday, demonstrators had milled about on Independence Square as they have every day since Dec. 1, when it was occupied and barricaded after a huge demonstration that drew hundreds of thousands. That rally was animated by public anger over a brief but bloody crackdown by the police against demonstrators the day before
