Protest by about 300,000 Ukrainians angered by their government's decision to freeze integration with the West turned violent Sunday, 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.
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.
The protesters also were infuriated by the violent dispersal of a small, opposition rally two nights before.
While opposition leaders called for a nationwide strike and prolonged peaceful street protests to demand that the government resign, several thousand people broke away and marched to Yanukovych's nearby office.