President Lukashenko is seeking a sixth term in office as the state TV exit poll showed he won almost 80 percent of the vote. But the main opposition candidate Svetlana Tikhanovskaya said she did not trust the released figures which gave her 7 percent.
She said: “I believe my eyes, and I see that the majority is with us.”
Thousands of protesters gathered in the country’s capital, Minsk, on Sunday as police used truncheons to beat demonstrators.
Protesters attempted to build barricades with rubbish bins.
Videos of Minsk’s streets show police using flash-bang grenades in an effort to disperse the protestors.
The capital’s centre is closed with military vehicles in place.
Internet services are also struggling or down all around the city.
Demonstrations also took place in other cities in Belarus including Brest, Gomel, Grodno and Vitebsk.
In Brest, police reportedly fired tear gas at protestors.
In a joint statement the president of Poland, Andrzej Duda, and the president of Lithuania, Gitanas Nausėda, called on Belarus to refrain from violence.
The statement read: “As neighbours of Belarus, we call on Belarusian authorities to fully recognize and uphold basic democratic standards.
“We urge to refrain from violence and call for respect of fundamental freedoms, human and citizen rights including the rights of national minorities and freedom of speech.”
Mr Lukashenko has been in power since 1994 but people in Belarus have become frustrated with his authoritarian rule.
He dismissed the coronavirus as “psychosis” and has refused to enforce any restrictions to limit the spread of the virus.
There are more than 68,500 confirmed COVID-19 cases in Belarus and 580 coronavirus related deaths.
Mr Lukashenko has said that his security services have been “light-handed” with protestors until now.
He promised that for those people who “break the law”, authorities will not be so forgiving.
Ms Tikhanovskaya entered the election in place of her activist husband who was jailed.
The protests in Belarus’ cities mark the country’s biggest opposition demonstrations in years.