Zimbabwe police fire tear gas, beat anti-Mugabe marchers: AFP

The rally -- which was authorised by a court -- was to demand electoral reforms before 2018 when 92-year-old President Robert Mugabe, who has ruled the southern African country for decades, will seek re-election.

An AFP correspondent saw armed police firing tear gas at protesters who were gathered on the fringes of Harare's central business district while waiting for the court ruling to allow the march to go ahead.

The protesters fought back by throwing stones at police while some set tyres ablaze and others pulled down the sign for a street named after Mugabe.

Some people caught up in the melee including children going to an agricultural show nearby ran for shelter in the magistrate's court building while riot police pursued the demonstrators and threatened journalists covering the rally.

The usually bustling pavements were clear of street vendors while some shops were shut.

- 'Victory for democracy' -High court judge Hlekani Mwayera allowed the march organised by 18 opposition parties including the Movement for Democratic Change led by Morgan Tsvangirai and the Zimbabwe People First formed this year by former vice president Joice Mujuru.

"We view this as victory for democracy," opposition spokesman Douglas Mwonzora said after the court ruling.

"The demonstration is going ahead (although) we know the police have already teargassed the venue."

The move to seek court backing came a day after police violently put down another march by opposition youths, firing tear gas and water cannon and beating them as they staged a protest against police brutality.

Police tried to "discourage" Friday's march, saying the anticipated crowd of around 150,000 would disrupt business and traffic.

But the opposition was defiant.

Former cabinet minister Didymus Mutasa, spokesman for the National Electoral Reform Agenda which groups political parties pushing for the reforms, said the march was to demand free and fair elections.

Zimbabwe's last elections in 2013 were won by Mugabe in a vote the opposition said was rigged.

Home Affairs Minister Ignatious Chombo warned on Thursday that the government would clamp down heavily on what it termed "Western-sponsored" protests seeking "regime change".

Zimbabwe has seen a mounting tide of violent protests over the past weeks, with demonstrators calling on Mugabe to step down.

Mugabe, who has been in power since 1980, has overseen an economic collapse that has caused food and cash shortages, with the country battling to pay public servants.

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