As the hundreds of armored officers converged from multiple directions on the encampment where thousands of people have been gathered for two weeks, a singer known as Ruslana led the protesters in singing the country's national anthem, the Washington Post reported.
It was not known if there were any injuries during the police action, which began about 1:30 a.m. with several blasts the newspaper said could have been caused by flash grenades. Police were removing barricades set up around the encampment while protesters still held the stage in the center, the Post said.
The bells of the nearby Mikhailovsky Cathedral were sounded after the police action began.
The Post said it was unclear if protesters still held City Hall, located several hundred yards away, or a trade union building they have used as an unofficial headquarters.
The move to break up the encampment came after Catherine Ashton, foreign policy chief of the European Union, and Victoria Nuland, U.S. assistant secretary of state, who were both in the Ukraine capital Tuesday, implored the two sides to reach a peaceful resolution.
Ukrainian President Victor Yanukovych and three former leaders had met Tuesday ahead of a national roundtable called to restore political stability, officials said.
Iryna Vannykova, spokeswoman for Yanukovych's predecessor, Viktor Yushchenko, said the meeting should be considered a first step in organizing the roundtable in which presidents, opposition leaders, young people and non-government organizations would meet, Interfax-Ukraine reported.
The Ukraine National Palace of Arts would serve as the site for the discussion of proposals from the public regarding the restoration of political stability, public peace and calm in Ukraine.
As the leaders met, demonstrators braved freezing temperatures to march along Kiev's snow-covered streets in protest of Ukraine's pro-Russian president, CNN reported.
Security forces in riot gear tried to herd demonstrators away from government buildings, but they refrained from a violent crackdown similar to ones Nov. 30 that drew international condemnation.
U.S. Vice President Joe Biden called Yanukovych Monday to urge him to talk with his opposition and avoid violence. European Commission President Jose Manuel Barroso talked to Yanukovych Sunday and also directed Ashton to fly Kiev to try to work things out.
The pro-Western demonstrations began several weeks ago when Yanukovych changed his mind over signing political and trade agreements with the European Union, saying Ukraine would be shortchanged and he would pursue closer ties with Russia instead.
On Monday, police broke down barricades protesters erected after progressing to the presidential administration building, pushing demonstrators back toward Independence Square.
Minor scuffles broke out and 10 demonstrators were injured, opposition party officials said. State media reported two police officers were hurt.
Masked men ransacked an opposition party's headquarters in a raid, Batkivshina Political Party leader Arseniy Yatsenyuk said.
The men, whom Yatsenyuk alleged were special forces officers, destroyed the his party's server room, CNN reported. Police denied being involved in the raid.
Also Monday, Yanukovych said he would support a call for talks with his opponents to work out a compromise.