By late Monday afternoon, reports emerged that police had encircled protest camps, dispersed demonstrators and stormed the main opposition party's headquarters. Earlier in the day, Ukrainian riot police in full gear had taken up position outside of Kyiv's city hall. The move came in the hours following a mass protest attended by several hundred thousand people calling for the ouster of President Viktor Yanukovych.

It was not immediately known how many demonstrators remained on Kyiv's Independence Square by the time that riot police had arrived on Monday. Previous estimates regarding the total number of protesters have varied, with the opposition putting it at 500,000 people. Separate observers put the figure close to 300,000.

The news agency DPA reported that police also closed a subway station in the downtown area. The report added that the Interior Ministry had begun threatening to bring charges against protesters if they broke the law.

On Sunday, some of the demonstrators tore down a statue of Lenin located 1.6 kilometers (1 mile) away from the square, then removing its head and beating it.

Bringing down the Lenin statue is seen as a symbolic move, rejecting President Yanukovych and closer ties to Moscow.

Demonstrations began over a week ago when Ukrainians took to the streets in angry protest of President Yanukovych's decision to abandon planned political and free-trade agreements with the EU. He further angered the opposition on Friday when he discussed the signing of a strategic partnership treaty with Moscow. Russian Prime Minister Vladimir Putin is eager for Ukraine to join its Customs Union, which some Ukrainians fear would be a first step toward rebuilding the Soviet Union.

Jailed ex-Prime Minister Yulia Tymoshenko has also called for his resignation and for Ukraine to seek a peaceful and legal end to his presidency.

Yanukovych vows compromise

Meanwhile, President Yanukovych issued a statement on his website on Monday in which he endorsed a proposal to seek a peaceful end to the mass protests. According to the statement, the first ex-Soviet President Leonid Kravchuk put forth the idea of holding an "all-national roundtable," which would be attended by Yanukovych and his three predecessors.

"On Tuesday, there is a planned meeting of four presidents of Ukraine…to discuss the key issues the country is facing," the statement read.

"Such a roundtable can become a platform for mutual understanding," it added.

Ashton to go to Kyiv

The announcement overlapped with a statement issued by EU Commissioner Jose Manuel Barroso. In response to the heightening tensions, the EU would send its top foreign policy chief, Catherine Ashton, on Tuesday to meet with leaders from all sides.

Barroso praised the Ukrainians' refusal to accept Yanukovych's anti-EU stance.

"If sometimes in Europe, some of us have doubts about how important these European values are, just look at Ukraine," Barroso said.

"When we see in the cold streets of Kyiv, men and women with the European flag, fighting for that European flag, it is because they are also fighting for Ukraine and their future."

kms/mz (AP, AFP, Reuters, dpa)