Nine months ago they were greeted as heroes, posing on their armoured vehicles for selfies with civilians overjoyed at their liberation from a moribund, corrupt, and violent dictator who had plunged the country into economic misery.

But on Wednesday night Zimbabwean troops were back on the streets of Harare - with bayonets fixed and in armoured cars to impose order with a blunt force that brought back unpleasant memories of Robert Mugabe’s reign.

And the fragile hopes that Zimbabwe's first elections since Mr Mugabe was overthrown would be peaceful went up in a pall of black smoke and tear gas.

Police said three people were killed in several hours of clashes between opposition supporters and security forces in Harare on Wednesday afternoon.

In a late-night press conference, Home Affairs Minister Obert Mpofu warned that the government "will not tolerate any of the actions that were witnessed today.

"The opposition... have perhaps interpreted our understanding to be weak, and I think they are testing our resolve and I think they are making a big mistake."