Thousands of protesters marched through Kiev on Sunday over Ukrainian President Viktor Yanukovych's refusal to sign an European Union trade deal.
Crowds gathered in a park before marching through the city to Kiev's Independence Square, the BBC reported.
At the square, protesters broke through metal shields surrounding a big Christmas tree under construction, Interfax-Ukraine reported.
Protesters also smashed windows in an effort to get inside Kiev's city hall building, the BBC said.
Yanukovych said he was "outraged" by the violence, the BBC said.
Jailed opposition leader and ex-Prime Minister Yulia Tymoshenko urged Ukrainians from all over the country to gather in Kiev Sunday for the protest.
"Fly, drive, walk to Kiev from all parts of Ukraine, but gather everyone on December 1," Tymoshenko said in a statement that was read aloud by her daughter on Saturday.
Protests in Ukraine started over a week ago after the government announced plans to suspend an EU association trade agreement.
Yanukovych said he was pressured by Russia to back away from the deal and that Ukraine could not afford to lose Russia as an ally.
On Saturday, at least 31 people were arrested at protests in Kiev.