Protesters try to break through police lines near the presidential administration building during a rally held by supporters of EU integration in Kiev, on December 1, 2013. Ukrainian opposition leaders called on Sunday for President Viktor Yanukovich and his government to resign at a rally of about 350,000 people, the biggest protest in the capital Kiev since the "Orange Revolution" of nine years ago. #

People attend a rally held by supporters of EU integration in Kiev, on December 1, 2013. Ukraine's interior minister warned protesters starting a pro-Europe rally in the capital Kiev on Sunday that police would respond if there were mass disturbances. #

Opposition protesters face riot police on November 29, 2013 during a demonstration in Kiev. Ukrainian authorities deployed hundreds of riot police to central Kiev where thousands of protesters gathered after President Viktor Yanukovych failed to salvage a key deal with the European Union. #

Protesters clash with police on Independence Square in Kiev early on November 30, 2013. Dozens of protesters were wounded in Ukraine's capital when police brutally dispersed demonstrators calling for President Viktor Yanukovych's ouster after he failed to salvage an EU deal. #

Wounded Reuters photographer Gleb Garanich, who was injured by riot police, takes pictures as riot police block protesters during a scuffle at a demonstration in support of EU integration at Independence Square in Kiev, on November 30, 2013. #

A protester waves a Ukranian flag from a moving car in Kiev, on November 30, 2013. Ukraine's political opposition said it would call a general strike to force the resignation of President Viktor Yanukovich's government after police used batons and stun grenades to break up pro-Europe protests. #

Lawmaker and chairman of the Ukrainian opposition party Udar (Punch), WBC heavyweight boxing champion Vitali Klitschko, (left, on the platform), waves a flag during a rally in downtown Kiev, on December 1, 2013. #

Demonstrators gather during a rally in downtown Kiev, on December 1, 2013. The mass rally in central Kiev defied a government ban on protests on Independence Square, in the biggest show of anger over President Viktor Yanukovych's refusal to sign a political and economic agreement with the European Union. #

Interior Ministry officers and riot police block the way of protesters near the presidential administration building during a rally held by supporters of EU integration in Kiev, on December 1, 2013. #

Protesters dig up stones during clashes with police outside the presidential administration building in downtown Kiev, on December 1, 2013. A protest by about 300,000 Ukrainians angered by their government's decision to freeze integration with the West turned violent, when a group of demonstrators besieged the president's office and police drove them back with truncheons, tear gas and flash grenades. Dozens of people were injured. #

Protesters clash with police at Presidential office in Kiev, on December 1, 2013. As many as 100,000 demonstrators chased away police to rally in the center of Ukraine's capital on Sunday, defying a government ban on protests on Independence Square. #

Men kneel down before a line of riot police near the presidential administration building during a rally held by supporters of EU integration in Kiev, on December 1, 2013. Ukrainian opposition leader Vitaly Klitschko, addressing hundreds of thousands of protesters in central Kiev, called on President Viktor Yanukovich and his government to resign, saying they had "stolen" Ukraine's dream of European integration. #

A protester with a chain clashes with police during the storming of the Viktor Yanukovych Presidential office in Kiev, on December 1, 2013. The crowd chanted "Revolution!" and "Down with the Gang" as it took control of Kiev's iconic Independence Square and steered a bulldozer within striking distance of police barricades protecting the nearby presidential adminstration office. #

A stun grenade explodes among protesters as they clash with police during the storming of the Viktor Yanukovych Presidential office in Kiev, on December 1, 2013. AFP reporters saw security forces outside the presidential building fire stun grenades and smoke bombs at a few dozen masked demonstrators who were pelting police with huge stones and what Ukrainian media said were molotov cocktails. #

A photographer stands in front of police members during clashes with pro-European Ukrainian demonstrators near the presidential administration office in Kiev, as outraged Ukrainians swarmed the city in a call for early elections meant to punish authorities for rejecting a historic EU pact, on December 1, 2013. Ukrainian media said President Yanukovych spent most of the day huddling with his most senior advisers at a secluded suburban residence. #

Protesters clash with police guarding the presidential administration building in downtown Kiev, on December 1, 2013. Police allowed the rally to proceed peacefully, but when a few thousand protesters tried to storm the nearby presidential administration building with a front loader, riot police used tear gas, truncheons and flash grenades to drive them back. Dozens of people with what appeared to be head injuries were taken away by ambulance. #

Kiev's landmark, the 50-meter-high (164-foot-high) Independence Column, seen through a hole in a barricade on December 2, 2013. Thousands of Ukrainian protesters besieged government buildings in Kiev and called for the ouster of the prime minister and his Cabinet, as anger at the president's decision to ditch a deal for closer ties with the European Union gripped other parts of the country and threatened his rule. #

Protesters sleep on the floor as others look through a window for possible police presence inside Kiev's city hall, on December 1, 2013. Ukrainian nationalist protesters broke into Kiev's city hall and were occupying at least part of the building during mass protests that drew several hundred thousands out on the streets to protest the government's decision to forgo an EU deal. #

Thousands of demonstrators march in the western Ukrainian city of Lviv on December 2, 2013. Ukrainian protesters blockaded administrative buildings and camped on Kiev's central square in a bid to oust the government after police brutality and a row over an EU pact plunged the nation into its worst political crisis in a decade. Demonstrators were newly incensed by a crackdown on an opposition rally calling for the resignation of President Viktor Yanukovych and his government. #