Armed men storm Ukrainian opposition offices, US voices concern

Masked men with guns in Kiev raided the party headquarters of jailed Ukrainian opposition leader Yulia Tymoshenko and took a computer server on Monday, spokeswoman Natalia Lysova said.

Lysova blamed police for the raid, but the police denied any involvement. Online newspaper Ukrainska Pravda said the raid was the work of the SBU state security service, which was unavailable for comment.

The raid occurred amid heightened tension in the Ukrainian capital after hundreds of thousands of people attended a protest rally on Sunday, which continued Monday, demanding the resignation of President Viktor Yanukovich, Tymoshenko's archrival.

The protesters, gathered in Kiev's Independence Square, are furious with the Yanukovich government for its decision to ditch a landmark pact with the European Union in favor of a trade deal with Moscow, Ukraine's Soviet-era overlord. Scores of riot police were dispatched to the area on Monday, stoking fears of a crackdown.

Yanukovich agreed on Monday to meet with the country's three former presidents to discuss how to end the political crisis. He said the round table would take place Tuesday.

Tymoshenko, whose fiery rhetoric galvanized protesters in the Orange Revolution of 2004 and '05 that denied Yanukovich the presidency then, is serving a seven-year sentence for abuse of office in a case condemned by many in the West as politically motivated.

Ukraine's opposition leaders have called on pro-Europe demonstrators to pressure Yanukovich to sack his government and drop plans for closer ties with Russia.

Also on Monday, U.S. vice president Joseph Biden expressed "deep concern" about the growing violence during a telephone call with Yanukovich. "Violence has no place in a democratic society and is incompatible with our strategic relationship," said Biden, according to a release from the White House.

The latest protests have escalated a weeks-long confrontation between authorities and protesters that has raised fears of political and economic instability in Ukraine, a former Soviet republic home to 46 million people.

Al Jazeera and wire services