Human rights groups said one person was killed and dozens were injured during a police crackdown on protests that followed the vote.
The country’s central election commission announced on Monday that all the ballots have been counted and Mr Lukashenko took 80.23% of the vote, while his main opposition challenger Sviatlana Tsikhanouskaya had only 9.9%.
The announcement may exacerbate tensions among opposition supporters who believe the results of the vote were rigged.
Thousands of people took to the streets in a number of Belarusian cities and towns on Sunday night, protesting against the early count suggesting Mr Lukashenko’s landslide victory.
Ms Tsikhanouskaya, a former English teacher and political novice, rejected the official figures, saying: “I will believe my own eyes – the majority was for us.”
Her supporters quickly took to the streets of the capital to protest what they saw as official manipulation of the vote.
They faced rows of riot police in black uniforms who moved quickly to disperse the demonstrators, firing flash grenades and beating them with truncheons.
The brutal crackdown followed a tense campaign that saw massive rallies against Mr Lukashenko, who has ruled the former Soviet nation with an iron fist for 26 years.
Mr Lukashenko has not yet commented on the election results or the protests.
Several other cities across the country saw similar crackdowns on protesters.
According to the Viasna human rights group, more than 100 protesters were detained, with the number likely to be much higher.
Interior ministry spokeswoman Olga Chemodanova said that police efforts to restore order continued overnight, but would not say how many people were detained.
On Monday morning, Belarus’s investigative committee opened a criminal probe into mass riots and violence toward police officers.
“What has happened is awful,” Ms Tsikhanouskaya told reporters.
An AP journalist was beaten by police and treated at a hospital.
At Minsk’s Hospital No 10, an AP reporter saw a dozen ambulances delivering protesters with fragmentation wounds and cuts from stun grenades and other injuries.
Two prominent opposition challengers were denied places on the ballot, but Ms Tsikhanouskaya, the wife of a jailed opposition blogger, managed to unite opposition groups and draw tens of thousands to her campaign rallies, tapping growing anger over a stagnant economy and fatigue with Mr Lukashenko’s autocratic rule.
Mr Lukashenko was defiant as he voted earlier in the day, warning that the opposition will meet a tough response.
“If you provoke, you will get the same answer,” he said.
“Do you want to try to overthrow the government, break something, wound, offend, and expect me or someone to kneel in front of you and kiss them and the sand onto which you wandered? This will not happen.”
Three journalists from the independent Russian TV station Dozhd were detained after interviewing an opposition figure and were deported.
The Organisation for Security and Cooperation in Europe, whose assessments of elections are widely regarded as authoritative, was not invited to send observers.
Ms Tsikhanouskaya had criss-crossed the country, tapping into public frustration over a worsening economy and Mr Lukashenko’s swaggering response to the coronavirus pandemic.
Belarus, a country of 9.5 million people, has reported more than 68,500 coronavirus cases and 580 deaths, but critics have accused authorities of manipulating the figures to downplay the death toll.
Mr Lukashenko has dismissed the virus as “psychosis” and declined to apply measures to stop its spread, saying a lockdown would have doomed the already weak economy.
He announced last month that he had been infected with Covid-19, but had no symptoms and recovered quickly, allegedly thanks to playing sports.
Yet for some voters, Mr Lukashenko’s long, hardline rule is a plus.
“He is an experienced politician, not a housewife who appeared out of nowhere and muddied the waters,” retiree Igor Rozhov said on Sunday. “We need a strong hand that will not allow riots.
