KIEV, Ukraine — Pro-European Union protesters occupying Kiev's city administration building said Monday that armed riot police had stormed the offices of the main opposition political party in downtown Kiev.
Meanwhile, several hundred riot police officers early Tuesday dismantled one of the last barricades set up by protesters more than a week ago to block off government buildings. Protesters had been given a Tuesday deadline to leave.
But more demonstrators reportedly were converging on Kiev's central Independence Square from around the city early Tuesday to bolster protesters' tent city, RIA Novosti said.
Witnesses also reported that authorities had cut power city hall after midnight in a bid to force protesters out.
The crackdown comes after hundreds of thousands of protesters filled the streets of the Ukrainian capital and other cities Sunday. It was the latest in a three-week-long series of so-called EuroMaidan protests sparked when President Viktor Yanukovych and his government refused to sign a long-expected pact with the 28-nation EU.
The protests started as a demand for closer ties with the EU and fewer with Russia but morphed into a more general anti-government movement after violent clashes with riot police late last month. The protesters are calling for the resignation of Yanukovych and his cabinet of ministers, and for the criminal prosecution of the police officers and officials responsible for the violent crackdown.
On Monday, Fatherland Party official Ostap Semerak told the Associated Press that troops broke into the party's headquarters and were walking along its corridors while others were climbing in through the windows. Fatherland is the party led by former Prime Minister Yulia Tymoshenko, jailed since 2011 over a controversial gas contract with Russia.
Semerak said the troopers confiscated some computer equipment and left.
The Freedom Party made similar claims, The Washington Post reported. A city police spokesman told the BBC that no actions had been taken by police officers at either party's headquarters; state security officials declined comment.
The main protests initially were centered in Independence Square. However, protesters in recent days constructed barricades to block the nearby streets leading to the main government buildings, including the president's administration building, the cabinet of ministers, and the parliament.
As of late Monday, no effort had been made to remove protesters from the administration building by force.
Roman Bilan, a 22-year-old student and protester, said that a crowd of about 500 protesters was trying to talk to riot police Monday at Independence Square, trying to ensure that they would not be forced away. Some protesters offered food to officers in an effort to curb police action.
The Interior Ministry said no action was being taken against protesters in the square, only those blocking access to government agencies. However, nearby public transportation stations remained closed in the wake of a bomb threat that authorities were investigating.
The wave of protests in Kiev may have included as many as a million people, according to reports. "We must press them with our numbers," said Bilan.
Yanukovych has agreed to meet with the country's three former presidents to talk about defusing the tense political crisis. The president said on his website that the meeting, labeled "a nationwide round table," will take place Tuesday.
But opposition parties late Monday rejected the calls for the talks, the Wall Street Journal reported.
The EU's top diplomat, Catherine Ashton, will be in Ukraine's capital Tuesday and Wednesday. EU Commission President Jose Manuel Barroso said she will try to help defuse "the very tense solution that Ukraine is living today."
In a phone call today with Yanukovych, Vice President Joe Biden "underscored the need to immediately de-escalate the situation and begin a dialogue with opposition leaders on developing a consensus way forward," the White House said in a statement.
Biden "noted that violence has no place in a democratic society and is incompatible with our strategic relationship," and "reaffirmed the strong support of the United States for Ukraine's European aspirations."
The heads of the opposition parties and leaders of the protests have called for continuing peaceful mass protest, but some protesters have argued for a less restrained approach.
"I may seem a bit provocative when I say it, but I think that the protest must get more radical," said Kateryna Kobko, 19-year-old English-language student from Kiev. "It won't be as peaceful as it was during the Orange Revolution in 2004. If you listen to what people say, they are in radical mood."
Kobko, who spent every day of the last two weeks at the protest, said she did it because Yanukovych's Party of Regions "is a malformed structure, and the system built on it must be fully destroyed."
Meanwhile, Bilan, a student from the Western Ukrainian city of Ivano-Frankivsk, said he came to Kiev with friends for a weekend to witness the protests. Impressed with the scale of the Sunday rally, he is now trying to decide whether to stay in Kiev for longer or to go back home and try to rally protesters there.
"I think the peaceful mass protest is the only way to go," he said as he ate a sandwich in a lobby of City Hall, one of several buildings seized by the protesters. He suggested that the current blockades could spread throughout the city.
Many protesters say they expected the government to attempt to break up the protests by force. Some at Independence Square said they were ready to fight the troops for the right to stay in the square.
Taras Berezovets, a political consultant based in Kiev, said Yanukovych likely will introduce a state of emergency.
EuroMaidan leaders condemned the actions of a group of nationalists who toppled a statue of the communist leader Vladimir Lenin on Sunday.
The men, many of them wearing masks and symbols of the nationalist Svoboda political party, tied cables around the statue's chest before pulling it down. The statue's head broke when it hit the ground. Kiev police are investigating and have not arrested anyone so far.
"They shouldn't perform such barbarism at a time when the whole world is watching Ukraine," said pop singer Ruslana Lyzhichko, one of the EuroMaidan protest leaders.
Others said it would provide the president with the additional justification to pursue a crackdown.
"It brings instability to the opposition alliance, because the Svoboda Party did it on their individual decision," said Berezovets, who added that the act "gives Yanukovych justification to introduce a state of emergency, as a response to the riots."
He added that Russia is the only side benefiting from the violence.
"Russia wants a weak Yanukovych and weak Ukraine," he said.