Belarusian president Alexander Lukashenko has been re-elected for a fifth term, following a campaign boycotted by the opposition.

Lidia Yermoshina, chairwoman of the Belarusian Central Election Commission, said Mr Lukashenko garnered 83.5 per cent in Sunday's vote. His closest contender trailed behind with less than 5 per cent.

Mr Lukashenko's share of the vote was an increase from 79.7 per cent in 2010.

About 100 opposition supporters held a peaceful protest march after polls closed to show their discontent.

Ms Yermoshina said all the ballots have been counted inside the country while the ballots cast at embassies abroad have yet to be counted.

The authoritarian leader of 21 years faced no serious competition in the election, which was boycotted by the opposition.

Opposition activists cast doubt on the high turnout, more than 87 per cent, as reported by authorities.

"The election commissions made up the results as they wished," opposition leader Anatoly Lebedko claimed.

"I'm amazed by the scale: they made up a staggering turnout with half-empty polling stations."

Ms Yermoshina of the election commission explained the high turnout by the fact that a lot of people opted to vote early.