Belarus President Alexander Lukashenko has warned protesters who challenge official election results will face a tough crackdown.
Dozens were injured and thousands detained hours after Sunday’s vote, when police brutally broke up mostly young protesters with tear gas and flash-bang grenades.
Rights activists said one person died after being run over by a police vehicle — which the authorities denied.
Election officials said authoritarian leader Mr Lukashenko won a sixth term in office with over 80% of the vote, while opposition challenger Sviatlana Tsikhanouskaya got 9.9%.
Ms Tsikhanouskaya dismissed the official results as a sham and vowed to dispute them, and the opposition is planning new protests in the capital, Minsk, and other cities.
The brutal police crackdown drew harsh criticism from European capitals and are likely to complicate Mr Lukashenko’s efforts to mend ties with the West amid tensions with his main ally and sponsor, Russia.
But Mr Lukashenko, whose 26-year iron-fisted rule has fuelled growing discontent in the ex-Soviet nation of 9.5 million, warned he would not hesitate to use force again to disperse the opposition demonstrations.
He argued that the protesters met a proportional response overnight after injuring 25 police officers and attempting to take control of official buildings in several Belarusian cities.
He said: “We will not allow them to tear the country apart. We wanted to make it a holiday for the people. But some wanted to spoil that holiday.”
The 65-year-old former state farm director asserted that the opposition was being directed from Poland and the Czech Republic, adding that some groups in Ukraine and Russia could also have been behind the protests.
“They are directing our sheep, who don’t understand what they are doing,” he said.
The Interior Ministry said 89 people were injured during the protests, including 39 law enforcement officers, and about 3,000 people were detained, including around 1,000 in Minsk.
It insisted that no one was killed during the protests and called reports about a death “an absolute fake”.
Ms Tsikhanouskaya, a 37-year-old former English teacher without any prior political experience, entered the race after her husband, an opposition blogger who had hoped to run for president, was arrested in May.
She has managed to unite fractured opposition groups and draw tens of thousands to her campaign rallies — the largest opposition demonstrations since the 1991 collapse of the Soviet Union.
She told The Associated Press: “We don’t agree with (election results), we have absolutely opposite information.
"We have official protocols from many poll stations, where the number of votes in my favour are many more times than for another candidate. We are gathering proof of falsification.”
The European Union has condemned the police crackdown and called for an immediate release of all those detained.