At least a dozen protesters and policemen were hurt when riot police prevented the crowd from marching towards the residence of President Alexander Lukashenko.

Baton-wielding riot police charged the protesters many of whom threw stones as they fled. A number of protesters were seen jumping into the city's Svisloch River to escape the police charge.

About 50 opposition supporters were arrested, representatives of the opposition Belarussian Popular Front told reporters.

The violence followed an authorised rally by up 20,000 anti-government supporters, many of them carrying banners saying they did not want to their country to be part of what they described as a new empire.

Others chanted slogans denouncing President Lukashenko as a dictator.

Show of strength

There were also calls for the government to say what it knows about the recent disappearance of three opposition politicians.

Correspondents say the rally was the biggest show of strength by opposition groups in recent years.

Mr Lukashenko's term as president was supposed to have ended last July, but it was extended by two years following a referendum that opposition politicians say was rigged.

They accuse him of ruling Belarus like a Soviet-era autocrat, and blame him for the disappearances and imprisonment of political opponents.