The Commonwealth's observer mission said Zimbabwe's security services used excessive force to break up protests in Harare over this week's election. Picture: Xinhua/Shaun Jusa

Harare - The Commonwealth's observer mission said on Thursday Zimbabwe's security services used excessive force to break up protests in Harare over this week's presidential election.

"We categorically denounce the excessive use of force against unarmed civilians," former Ghanaian president John Mahama said in a statement on behalf of the Commonwealth.

The Commonwealth also urged the Zimbabwe Electoral Commission to expedite the announcement of the results of the presidential vote. 

Zimbabwe police said three people were killed in Harare on Wednesday as soldiers dispersed stone-throwing opposition supporters who accused the ruling party of trying to rig Monday's presidential election.

The deployment of soldiers and their beating of unarmed protesters set back President Emmerson Mnangagwa's efforts to shed Zimbabwe's pariah status after decades of repression under Robert Mugabe, who was ousted in a coup in November.

Police spokeswoman Charity Charamba told state broadcaster Zimbabwe Broadcasting Corporation (ZBC) that the three people killed in the clashes had yet to be identified.

Gunfire crackled as troops, backed by armoured vehicles and a military helicopter and some with their faces masked, cleared the streets of opposition protesters.

The unrest started soon after Nelson Chamisa, leader of the opposition Movement for Democratic Change (MDC), declared that he had won the popular vote.

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