Thousands of Belarusians protesting what opposition says was a rigged presidential election smashed windows and doors of government headquarters in central Minsk Sunday night.
The protesters tried to storm the building, which also houses the parliament, but were met by riot police ready to act.
Around 30,000 Belarusians defied President Alexander Lukashenko and marched in central Minsk Sunday.
Police used noise grenades to try and drive away an initial group of protesters. They also beat and seriously injured opposition candidate Vladimir Neklyayev, who was taken to a hospital unconscious.
Police flooded Independence Square in central Minsk with water in Arctic-like temperatures, hoping to turn it into an unsafe ice rink.
But that did not stop thousands from massing, chanting pro-democracy slogans and waving European Union flags.
While casting his vote earlier Sunday, Mr. Lukashenko denounced the opposition and said there would be no one on the square that night.
Early exit polls show him winning at least 72 percent of the vote over nine rivals, which would give him a fourth five-year term.
But the opposition says authorities urged voters to cast their ballots before election day, which it says opens the door to massive fraud.
Former U.S. President George W. Bush called Mr. Lukashenko "Europe's last dictator" for suppressing free speech, human rights and rigging past elections.
The European Union also maintains sanctions against some Belarusian officials.
Mr. Lukashenko has recently been feuding with long-time ally Russia over gas and oil prices and has spoken of closer ties to the West.
But European Union foreign ministers have said they are concerned with a lack of progress towards democracy and human rights in Belarus.