Protesters rally in Minsk on Sunday to denounce an election they say was rigged. (Sergei Grits/Associated Press)Thousands of opposition supporters tried to storm Belarus's main government building in Minsk after Sunday's national election, which a government exit poll showed — and official results later confirmed — President Alexander Lukashenko had won by a landslide.

About 40,000 opposition supporters rallied in central Minsk to call for the longtime authoritarian leader to resign. But the crowd, the largest opposition rally since 1996, was dispersed by baton-wielding police. Dozens of protesters were injured in clashes with riot police and their leader, as well as two other candidates, were beaten.

Lukashenko garnered 79.1 per cent of the vote, while Grigor Kostusev won 4.2 per cent, according to the Minsk-based EcooM research centre. Official results released later by the state electoral commission showed Lukashenko won his fourth term in office with 79.7 per cent of the votes, Reuters reported.

Three of the candidates who ran against Belarus's authoritarian president were arrested and the top opposition leader Vladimir Neklyayev was taken from a hospital by unknown men in civilian clothes, The Associated Press reported, citing activists. No further details about the arrests were provided.

During the campaign, many diplomats and political analysts speculated that the contest results had been determined beforehand. Opposition groups said their members were intimidated a number of times.

Belarus President Alexander Lukashenko garnered 79.1 per cent of the vote, while Grigor Kostusev won 4.2 per cent, according to the Minsk-based EcooM research centre. (Associated Press)

Rights activists reported that five senior campaign workers and 27 opposition activists had been detained since Saturday. Police refused to comment.

Candidates beaten up

After the polls closed, Neklyayev was attacked by unknown men while leading hundreds of supporters to the protest rally in Minsk, said his aide, Anastasia Alexandrovich.

The candidate's wife later said riot police had attacked her husband.

Neklyayev, 64, lost consciousness after being beaten and was taken to hospital for treatment of head injuries, Alexandrovich said.

Later, seven men wrapped Neklyayev in a blanket in his hospital bed and carried him outside as his wife screamed, locked in a neighbouring room. His whereabouts are unknown, his aide said.

After the polls closed, thousands of opposition activists converged as planned on October Square in Minsk, but most of the square had been flooded to make an ice-skating rink and pop music boomed from loudspeakers.

The protesters then set off along the main avenue toward Independence Square, where the main government building is located. By late Sunday, troops cleared the square of the 2,000 remaining protesters.

Lukashenko has ruled the ex-Soviet republic since 1994 and has been characterized as Europe's last dictator.

He fully dominates this eastern European country of 10 million people and is popular with large portions of the population for preserving much of the Soviet system.

The government allows no independent broadcast media and 80 per cent of industry is state-controlled.

During the campaign, the nine candidates challenging Lukashenko for the presidency were allowed time for debates on state television and radio.

However, Andrei Sannikov, one of the opposition candidates and a former deputy foreign minister, accused the government of blocking opposition internet sites and cellphones.

With files from The Associated Press