Belarusian President Alexander Lukashenko won 80.23% of the vote in the country's presidential election, while his main rival won 9.9%, according to preliminary results.
Belarusian opposition candidate Svetlana Tikhanovskaya had earlier refused to accept state media projections that gave her a similarly limited vote share.
Police violently cracked down on protests that erupted in major cities on Sunday night after the polls closed.
Belarusian authorities detained about 3,000 people at protests throughout the country following the presidential election, the Interior Ministry said on Monday in comments carried by the Russian news agency Interfax.
"Of them about 1,000 were in Minsk and more than 2,000 were in other regions," the Interior Ministry said. Protests were reported at polling stations and in central streets in 33 localities on Sunday night, it said.
Lidia Yermoshina, head of the Belarusian Election Commission, announced on Monday that Tikhanovskaya had come second, with the other three candidates receiving fewer than 2% of the vote.
Turnout was put at 84%.
Over 50 people were detained in Minsk and more than 120 had been detained nationwide in the unrest, human rights organization Viasna said on Sunday.
Lukashenko, 65, has led the former Soviet republic in Eastern Europe, between Russia and EU member Poland, for a quarter century, tolerating little dissent.