Figures released by the election commission on Monday gave Lukashenko 80% of the vote.
Svetlana Tikhanouskaya, a former English teacher who emerged from obscurity a few weeks ago to become Lukashenko's main rival, won 9.9% of the vote, the data showed.
At least one person was killed after being knocked over by a police van and dozens were injured in the clashes that began after polling stations closed on Sunday, a representative of the rights group Spring 96 told Reuters.
A former Soviet collective farm manager, Lukashenko has ruled the country since 1994, but faces the biggest challenge in years to keep his grip on power with some voters believing strongly that it's time he stood down.
He has cast himself as a guarantor of stability but has battled a wave of anger over his handling of the COVID-19 pandemic, the economy and his human rights record.
Tikhanouskaya entered the race after her husband, an anti-government blogger who intended to run, was jailed.
Her rallies have drawn some of the biggest crowds since the fall of the Soviet Union in 1991.
Foreign observers have not judged an election to be free and fair in Belarus since 1995.
A severe crackdown on protests could hurt Lukashenko's attempts to mend fences with the West amid fraying ties with traditional ally Russia, which has tried to press Belarus into closer economic and political union.
Human rights groups say more than 1,300 people were detained in the crackdown ahead of the election, including independent election observers and members of Tikhanouskaya's campaign team.After casting his vote on Sunday, Lukashenko denied imposing repressive measures as "fake news or far-fetched accusations."