Landmark elections in the DR Congo have been marred by isolated incidents of violence and there was a tense standoff between the police and supporters of the main opposition candidate.
Violence erupted at four polling stations in the south of the vast country, which held its second elections since a war that killed more than 5million people.
Masked gunmen attacked a polling station in the southern mining province of Katanga. Three of them were killed by security forces.
Locals burned down three polling stations in the neighbouring opposition heartland of West Kasai, and an election observer was badly injured in crowd violence there, Congolese electoral monitoring group Renosec said.
In Kinshasa, police blocked opposition leader Etienne Tshisekedi and thousands of his supporters on a main road as the presidential candidate went to cast his vote.
Tshisekedi, incumbent Joseph Kabila's main election rival, was forced to turn around as police cars and armoured vehicles blockaded the road.
After making a U-turn, Tshisekedi voted at Lumumba Institute before about 150 riot police and two armoured police trucks arrived.
"Of course I'm going to win the elections," Tshisekedi told journalists as he left the school.
Voters headed slowly - and for the most part peacefully - to the polls elsewhere in the country, which was devastated by a 1998-2003 war.
The capital Kinshasa, where at least two people were killed in violence on Saturday, was generally calm.
But tensions were high after a last-minute scramble to prepare for the vote, with Kabila alleging irregularities and bias in the electoral commission.
"Three people were killed, seven were arrested and five handed themselves over after being surrounded by the army," said Katanga province governor Moise Katumbi.
"Everything is under control," he said.
In West Kasai, locals burned down three polling stations and police fired shots to disperse about 100 people who gathered outside the mayor's office in the town of Mbuji-Mayi, complaining that they did not know where to vote.
One female Renosec observer was seriously injured after being attacked by crowds fearing electoral fraud in Kananga, said Francois Badibanga, spokesman for the election-monitoring organisation.
The polls - which pit Kabila against 10 rivals while more than 18500 candidates compete for 500 seats in parliament - will test progress towards stability after decades of misrule and two wars in the last 15 years.
Kabila came to power when his father, Laurent, was assassinated in 2001. Joseph won the 2006 poll.
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