In the Mozambican capital, Maputo, riot police have fired tear gas at opposition protesters who say last week's local elections were rigged in favour of the ruling Frelimo party.
Dozens of people have suffered minor injuries while fleeing the police.
"They didn’t need to do this, after all, isn’t this democracy? We are marching peacefully and we don’t want problems with anyone," said one protester.
Analysts have questioned whether Mozambique's state-owned electricity company deliberately cut off power to help sabotage the election.
"Maputo City is not known for frequent power cuts. It's funny how exactly on election day, at the time of vote counting, the most populated neighbourhoods went dark for hours. It happened in previous elections as well," said Human Rights Watch researcher Zenaida Machado.
The main opposition Renamo party has failed to win any municipalities despite governing seven before the polls.
On Thursday, local media reported that two Mozambican courts annulled the results of elections in Chokwe district in southern Gaza province and Cuamba district of the northern Niassa province after they found irregularities in the process.
Renamo leader Ossufo Momade says the protests won't stop until the "electoral truth" is uncovered.