A government crackdown in Zimbabwe after Monday's elections has prompted international calls for restraint.
The UN and former colonial power the UK both expressed concern about the violence, in which three people were killed after troops opened fire.
Parliamentary results gave victory to the ruling Zanu-PF party in the first vote since the removal in November of long-time leader Robert Mugabe.
But the opposition says Zanu-PF has rigged the election.
The result of the presidential vote is not yet known.
The opposition MDC Alliance insists its candidate, Nelson Chamisa, beat the incumbent President Emmerson Mnangagwa.
Zanu-PF, which has been in power for 38 years since the country gained its independence, denies there has been any rigging and has called for calm.
The government was in talks with Mr Chamisa to diffuse the crisis and "we must maintain this dialogue in order to protect the peace we hold dear", President Mnangagwa said.
He called for an independent investigation to ensure that those behind Wednesday's violence were brought to justice, Mr Mnangagwa added in a series of tweets.
UN Secretary General Antonio Guterres urged Zimbabwe's politicians to exercise restraint, while UK foreign office minister Harriett Baldwin said she was "deeply concerned" by the violence.
The US embassy in Harare urged the army to "use restraint" on Twitter, saying the country had an "historic opportunity" for a brighter future.
Human rights group Amnesty International's acting secretary general Colm O Cuanachain said in a press release that the "militarisation" of the election aftermath was "muzzling freedom of expression, association and assembly".
"People must be guaranteed their right to protest," he said.
No violence was reported on Thursday. A truckload of armed policemen and soldiers were driving around the city shouting, "Behave yourself, people of Zimbabwe."
BBC
