As counting gets underway, both sides have accused each other of trying to rig the vote. Vote counting is under way in the Democratic Republic of Congo where presidential and parliamentary elections have been taking place.
Both opposition and government have accused each other of vote rigging.At least four people died after gunmen attacked polling stations in the second city, Lubumbashi, officials say.
It is the second elections since the end of civil war eight years ago, in which four million people died.
Both President Joseph Kabila, 40, who has been in power for 10 years, and the veteran opposition leader, Etienne Tshisekedi, 78, said they were confident of victory.
Mr Tshisekedi has accused Mr Kabila of planning to rig the election.
In the opposition stronghold of West Kasai, polling stations were reportedly set on fire by voters angry at long delays. In the same province, there were unconfirmed reports of ballot boxes being full as polling opened.
A heavy police presence helped ensure the capital, Kinshasa was generally peaceful during the day, but after nightfall, there were numerous reports of shooting.
The BBC's Will Ross reported from a polling station in Kinshasa, where, he said, representatives from several opposition parties were not allowed to witness the counting of ballot papers.
In other parts of the country, the governing party accused the opposition of fraud.
He says unless people perceive the process to be free and fair, there is a danger this election will not pass off smoothly and with both candidates saying they are confident of victory, that stance could fuel the tension.
In the eastern city of Goma, Cindy McCain, the wife of United States Senator John McCain, is leading a delegation of poll watchers.
She said that in one polling station, they found ballot boxes were already a third full when they arrived at dawn, according to the AP news agency.
About 22,000 UN peacekeepers are stationed around the country - they are expected to help prevent any outbreaks of violence.
Helicopter deliveries
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Gunmen have attacked two polling stations in Lubumbashi, causing several fatalities.
Panic-stricken voters fled, screaming and crying.
They blamed pro-secessionist fighters for the attacks, but said they were determined to vote.
Lubumbashi is the main city in the mineral-rich Katanga region which was hit by a secessionist war after independence more than 40 years ago.
Will Ross, Kinshasa:
It was not really a ballot paper - more like a broadsheet newspaper. For the national assembly election in central Kinshasa there were 13 pages packed with candidates' faces.
The heavy rain may have slowed down the stream of voters but there is still a palpable desire to make their choices count.
Some stations opened late but the grumbles from voters were no greater than at other elections I have covered - the big question is how the inaccessible rural areas fared.
BBC reporters around DR Congo
Mamadou Moussa Ba, Lubumbashi:Gunmen have attacked two polling stations in Lubumbashi, causing several fatalities.
Panic-stricken voters fled, screaming and crying.
They blamed pro-secessionist fighters for the attacks, but said they were determined to vote.
Lubumbashi is the main city in the mineral-rich Katanga region which was hit by a secessionist war after independence more than 40 years ago.
Will Ross, Kinshasa:
It was not really a ballot paper - more like a broadsheet newspaper. For the national assembly election in central Kinshasa there were 13 pages packed with candidates' faces.
The heavy rain may have slowed down the stream of voters but there is still a palpable desire to make their choices count.
Some stations opened late but the grumbles from voters were no greater than at other elections I have covered - the big question is how the inaccessible rural areas fared.
Voting was extended in some areas because of the late start as election officials scrambled to get ballot papers distributed to all 60,000 polling stations in the country - which is two-thirds the size of Western Europe and has little transport infrastructure.
The BBC's Mamadou Moussa Ba in the south-eastern mining capital of Lubumbashi says gunmen - suspected to belong to a secessionist movement - attacked two polling stations in the city. AFP news agency quotes a military spokesman as saying two policeman and a civilian were killed and two soldiers wounded.
The governor of the local Katanga province, Moise Katumbi, told Reuters news agency that three of the attackers had been killed and seven arrested.
Our reporter says there were lengthy delays at some polling stations, which failed to open six hours after voting was due to start, although polling began on time in other areas.
President Kabila comes from the Katanga region around Lubumbashi and it has been a stronghold of the governing party.
But Mr Tshisekedi is mounting a strong challenge and tension there has run high in recent weeks.
'Who will pay?'
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DR Congo polls in numbers
- More than 30 million voters
- More than 19,000 parliamentary candidates
- 500 parliamentary seats
- MPs paid $6,000 (£3,887) a month
- The Kinshasa ballot will be a 56-page booklet of more than 1,500 candidates
- 11 presidential candidates
- 4,000 tonnes of ballot papers
- 61 helicopters and 20 planes are delivering the election material
Mr Tshisekedi's Union for Democracy and Social Progress (UDPS) party said police blocked his route as he was going to a polling station in Kinshasa, forcing him to go to another voting centre to cast his ballot.
In West Kasai, anger at the long delays were fuelled by reports that stuffed ballot boxes had been found, a UN source told the AFP news agency.About 15 polling stations were burnt in this region, where Mr Tshisekedi has long enjoyed strong support.
In Kinshasa, there were also reports of long delays while voter turnout was hit by torrential rain.
Some voters told the BBC they were unable to cast their ballots - either because they could not find their names on the electoral register or because someone had already voted in their place.
In the north-eastern town of Kisangani, Jasper Mulungi protested: "I was here at 5am and now they are telling me to move to another polling centre about 20km away. Who will pay for my transport?"
As well as the 11 presidential candidates, more than 18,000 are vying for seats in the 500-member parliament.
In some areas, the ballot paper ran to several pages and resembles a newspaper because there are so many parliamentary candidates.
This is likely to have caused some confusion in a country where one-third of adults cannot read or write.
The last election, in 2006, was marred by weeks of street battles led by supporters of the losing candidate, Jean-Pierre Bemba.
A former rebel leader, he is now on trial for alleged war crimes at the International Criminal Court in The Hague.
Inside DR Congo
The Democratic Republic of Congo covers 2,344,858 square km of land in the centre of Africa, making it the 12th largest country in the world.
Source: BBC News, 28 November 2011 Last updated at 23:07 GMT
Source: BBC News, 28 November 2011 Last updated at 23:07 GMT
