Masked demonstrators in Kyiv have toppled a statue of the Soviet Union's founder, Vladimir Lenin, as protests demanding senior government resignations and fresh elections continued to rage in the Ukrainian capital.
"Goodbye, communist legacy," Andriy Shevchenko, an opposition lawmaker, wrote on Twitter.
The spokesman of Ukrainian Prime Minister Mykola Azarov called the felling of the statue "barbarism."
Opposition leaders denied any link to the action.
RFE/RL correspondents in Kyiv reported late on December 8 that more than 100,000 demonstrators had swarmed into the neighborhood that includes the parliament, presidential administration, and government headquarters in an attempt to blockade the area.
The move came after Nikolai Katerinchuk, an opposition lawmaker from the Batkivshcina (Fatherland) party, called for "total mobilization" by hundreds of thousands of demonstrators in and around Kyiv's Independence Square in order to control the city.
Reports say Katerinchuk told the crowd: "We must take control of each street, each courtyard, each corner" and "install checkpoints at all roads leading to the city" in order to "control the movement of police and armed forces.
Demonstrators were setting up protest tent camps on the streets of the government district and erecting barricades as the area being blocked continued to expand.
The Fatherland party's Arseniy Yatsenyuk later called on protesters to return to the hub of protests for more than two weeks, downtown Independence Square, by 5 a.m. on December 9.
European Commission President Jose Manuel Barroso stressed "the need for a political" solution during a telephone conversation with President Viktor Yanukovych, who also discussed the crisis with UN Secretary-General Ban Ki-moon.
A UN statement said Ban "expressed his grave concern about the situation in Ukraine, emphasized that there must be no resort to violence and appealed for peaceful dialogue among all parties concerned."
WATCH: A statue in downtown Kyiv is torn down on the heaviest day of protests since the Ukrainian government signaled its decision to back out of talks for an EU Association Agreement more than two weeks ago:
The protesters are vowing to continue occupying Kyiv’s government district until new parliamentary and presidential elections are called.
Their actions follow a major pro-EU demonstration on Independence Square on December 8 that attracted hundreds of thousands of people angered by Yanukovych's recent snub of the European Union in favor of improved ties with Moscow.
Security forces from Ukraine's Interior Ministry have set up cordons around the government headquarters, the parliament, and the president's office -- as well as other key government buildings and smaller buildings that house political-party offices.
A network of underground tunnels built during the Soviet era connect many of the government buildings and political-party headquarters to each other within the government district -- which is on a hill overlooking Independence Square and Kyiv's city center.
Prime Minister Azarov has repeated a call for protesters to unblock government buildings, according to Interfax-Ukraine.
A spokeswoman for Ukraine's Security Service reportedly said earlier that the service had opened a criminal probe into alleged attempts by "certain" politicians to seize state power.
RFE/RL correspondent Andriy Bashtoviy said the size of the protest crowd late on December 8 appeared to be large enough that they were preventing government officials from being able to reach the tunnel entrances in order to get to their offices.
Meanwhile, RFE/RL correspondents estimated about 500,000 protesters remained gathered in and around Independence Square in central Kyiv, with many roads in that area also blocked off by the crowd, cars and buses, and protest tents.
The day saw wildly varying estimates of crowd numbers, from 60,000 by police to "nearly a million," in the words of Vitali Klitschko, the leader of the opposition Udar (Punch) party.
WATCH: A video shot by RFE/RL Ukrainian Service correspondent Andriy Dubchak of the "EuroMaydan" antigovernment protests in downtown Kyiv on December 8 from atop a metal-frame "Christmas tree" on Independence Square suggested crowd figures were far greater than the 60,000 people that police claimed.
RFE/RL correspondent Tom Balmforth described the crowd as disciplined and said patrols of protesters had been organized to try and preempt any efforts by "provocateurs" to give police grounds to forcibly disperse the crowd, as happened a week ago at the same spot.
Jailed former Prime Minister Yulia Tymoshenko issued a statement from prison that was read out to the December 8 rally by her daughter, Yevhenia. In it, Tymoshenko called for Yanukovych's ouster, saying he "has lost legitimacy as president."
WATCH: Ukrainian opposition leaders address hundreds of thousands of people who turned out for the antigovernment rally in Kyiv on December 8:
Tymoshenko was jailed for seven years on abuse-of-office charges widely condemned as politically motivated.
Her condition and Kyiv's failure to allow her to seek medical treatment abroad have kept tensions simmering between Yanukovych's administration and Brussels.
By December 8, Kyiv's Independence Square had been the main focus of nearly three weeks of daily protests.
The demonstrators initially were protesting President Yanukovych’s decision last month to suspend work on an association and free-trade accord with the EU.
Yanukovych defended that decision by saying the accord with the EU would damage close trade ties with Russia.
But the protesters have been calling for new parliamentary and presidential elections since the violent police crackdown against demonstrators on November 30 left dozens injured.
The anger over the decision by Ukraine's political leadership to balk at an EU Association Agreement has produced the largest public demonstrations since the country's Orange Revolution in 2004-05, which was sparked by a rigged presidential election won by Yanukovych.
Based on reporting by RFE/RL correspondent Tom Balmforth and RFE/RL's Ukrainian Service correspondent Andriy Bashtoviy in Kyiv, with reporting by AP, Reuters, AFP, and BBC