Mozambique's opposition party on Friday accused the police of using teargas to disperse its supporters in the central Gorongosa region, where the ruling party's victory in municipal polls is disputed.
"Police are being manipulated to use teargas against us," the Mozambique Democratic Movement (MDM) candidate Daniel Missasse told AFP during the protest.
"We are holding a peaceful march," he said, adding, "We don't want trouble with anyone."
The opposition supporters were marching to the offices of the National Electoral Commission, to register a complaint of fraud by the ruling Mozambique Liberation Front (Frelimo) party.
Provisional results gave Missasse only 43 per cent of the vote.
Frelimo has dismissed the fraud allegation as "pure lies".
Frelimo's spokesman Damiao Jose said the MDM was finding it difficult to accept defeat.
The restive Gorongosa region was used by rebels of the Mozambican National Resistance (Renamo) and its leader Afonso Dhlakama as its base, before it was seized by the army last month.
Renamo, which had for long time been at loggerheads with government, had threatened to disrupt the polls.
Voting on Wednesday went off without major reports of violence, but on Thursday a local musician who was performing at an MDM victory party in the town of Quelimane was shot, allegedly by one of the governor's guards.
"One of the residential guards of the governor... took a rifle and shot him in the head," said the mayor of Quelimane, Manuel de Araujo.
"The bullet went in his face and out of his neck. He died there, instantly."
Quelimane is one of two provincial capitals where provisional election results show a convincing MDM win.
Frelimo, which has won all elections since the end of Mozambique's civil war in 1992, is currently leading the vote.