Opposition and government supporters clashed in Guinea's capital on Friday, throwing rocks, smashing car windows and burning tyres in the latest outburst of ethnically-tinged political violence.
Tensions are high in the coup-prone West African state over long-delayed parliamentary elections, which the opposition says the government wants to rig.
Protesters blocked Conakry's main bridge and barricaded other roadways, with running clashes forcing local residents to lock themselves indoors, according to witnesses, who said security forces were deployed but did not intervene.
"They are throwing everything they get their hands on," said Ibrahima Keita, an army officer. "There are many wounded here at the gendarmerie and the Red Cross is coming to get them."
One witness told Reuters the fighting started after ethnic Peul merchants found their market stalls ransacked Friday morning, and blamed ethnic Malinkes .
Guinea's opposition is mostly made up of Peul, the country's largest ethnic group which has long complained of being politically sidelined by the Malinkes.
President Alpha Conde, a Malinke, was elected in late 2010 in a vote that ended military rule but which was tainted by deadly riots and opposition complaints of fraud.
Since then, the opposition has staged sporadic protests in Conakry and other towns, several of which have triggered violent security crackdowns.
Conde's government is trying to organise legislative elections, but progress has been slowed by opposition worries that the electoral body is biased.
The election is the last major step in the transition back to civilian rule in the former French colony since a 2008 coup, and is key to unlocking millions of dollars in frozen aid.
Guinea is the world's top supplier of the aluminium ore bauxite and holds rich deposits of iron ore, but political turmoil has cooled the investment climate.
The opposition wants the government to fire South African firm Waymark, which won a contract to handle the electoral register for the vote.
"We demand an international bidding process for finding a new technical operator," said Aboubacar Sylla, a spokesman for the opposition.
In a major concession, Conde accepted the resignation of the head of the electoral commission earlier this month and agreed to restructure the commission to better represent the opposition.
Sylla said the move was a step in the right direction but did not fully address concerns that the elections would be flawed. An opposition march on Thursday over the election passed mostly peacefully.
While Conde's government has said it hopes to hold the polls by the end of this year, technical experts and Western diplomats say an election would not be physically possible before March at the earliest.
The International Monetary Fund is set to decide by the end of the month if Guinea is eligible for some $2 billion in debt relief under the Heavily Indebted Poor Countries programme, which would free up funds for development.