Police in Kinshasa, the capital of the Democratic Republic of Congo, have fired tear gas to disperse several hundred opposition supporters who accuse the electoral commission of fraud in the run up to elections later this year.
The protest is the latest sign of growing tension in Congo before presidential and parliamentary polls in November, the second set of elections since the last war ended in 2003.
The demonstrators accuse President Joseph Kabila's party of rigging polls in his favour by allowing for the multiple registrations of voters ahead of the elections.
The country's electoral commission has admitted that there were 20,000 duplicate registrations on a voter list of about 32 million people.
Fears over delays and spiralling costs for the poll are also mounting as much of the election equipment is still abroad and international backers, who played a prominent role in elections in 2006, are taking less interest in this year's poll.
Heavy police presence
The demonstration had been authorised by city officials but police intervened when protesters disrupted traffic and became violent, according to General Charles Bisengimana, Congo's chief of police.
"One policemen was injured. They ransacked several cars and pillaged some shops, that's why the police used [tear gas] grenades to disperse them," Bisengimana told the Reuters news agency.
A heavy police presence was still visible outside the electoral commission several hours after the demonstrators had been dispersed.
Facing a still divided opposition, incumbent President Joseph Kabila is seen as favourite for re-election, although analysts say many voters, even those in his eastern strongholds, are disappointed with a lack of progress since 2006.