Riot police in armored carriers were deployed in two of Harare's restive townships on Monday night amid long delays in issuing Zimbabwe's election results which have raised tensions.
A resident of one of the townships, opposition strongholds, said a convoy of riot police in about 20 vehicles moved through the area.
"There are a lot of patrols here," said the resident, adding people had been told to stay off the streets.
Concern grew that long delays in issuing the election results hid attempts by President Robert Mugabe to cling to power by rigging.
More than 48 hours after polls closed, only 66 of 210 parliamentary constituencies had been declared, showing Mugabe's ZANU-PF party one seat ahead of the main opposition MDC. Two of his ministers lost their seats.
Zimbabwe is on the brink of being the second African nation in less than six months to face chaos following elections. In December, riots broke out in Kenya following what many thought were rigged elections. That crisis was averted when the two opponents in the election agreed to a powersharing arrangement. More than one thousand people died in the fighting that broke out prior to the agreement.