Four opposition challengers to Democratic Republic of Congo's President Joseph Kabila have called for election results to be rejected, accusing authorities of systematic fraud.
Candidate Vital Kamerhe, a former government minister, said on Tuesday that ballots had been marked before the vote in favour of Kabila, and some voters prevented from entering polling stations during Monday's chaotic presidential and parliamentary elections.
Three other candidates also urged the Congolese not to accept any results from the vote, saying technical problems and fraud meant they would not be credible. However Kabila's top rival, Etienne Tshisekedi, did not join their call and his party said it was confident he would win.
"There can be no doubt as to the scale of the fraud, deliberately planned by those in power with the connivance of the national election commission," Kamerhe wrote in a letter to Kabila, the election commission and international bodies.
"Police chased witnesses from polling stations before counting could start," he said, citing reports by international observers and others that security forces took control of voting stations in Kinshasa.
"These elections must quite simply be annulled."
Monitors have reported widespread election fraud and chaos as votes were counted Tuesday after a campaign and polling day marred by deadly violence.
Al Jazeera's Yvonne Ndege, reporting from Kinshasa, said: "In some places, you had voters showing up to find that their names were not on the electoral register.
"And in other places, it was just the slowness of the vote itself," said Ndege, adding that many people were outside polling stations, waiting to vote.
Mounoubai Madnodje, spokesman for the UN mission in Congo known as MONUSCO, said the UN was still delivering electoral materials on Tuesday to some areas which have yet to vote, including the central province of Bandundu.
Fraud allegations had been raised ahead of the polls
Al Jazeera's Azad Essa said the eastern city of Goma was bustling with activity on Tuesday after a long weekend of last-minute campaigning and voting the previous day.
Security remained around polling stations as counting continued throughout the day, and police patrols on flat bed trucks could be seen intermittently around the city.
Scores perused polling stations to take a peek at the provisional results handwritten on paper bills posted on office walls and windows inside polling complexes.
The disturbances in Kinshasa and in the neighbouring province of Katanga seemed to have little effect on daily routines on the ground in Goma, though one voter at a polling station told Al Jazeera that the troubles in Katanga "were Kabila's people trying to start a war" because of the perceived success of opposition candidate Kamerhe.
Across the nation, voters complained that confusion over voter lists made it difficult for many to know where to vote.
The election commission said the ballot was "satisfactory".
Tensions flared and violence was reported at many polling stations during voting, over allegations of fraud.
"Here in Kinshasa we don't have any confidence in the process but in this polling station we have worked hard [to stop fraud]," said Henriette Kilonda, an election official at the Ecole de la Gare voting centre in Gombe, central Kinshasa.
It was too early to ascertain any voting trends and full provisional results are not due till December 6.
Violence and intimidation
Anaclet Tshimbalanga, the president of TDH, a human rights group in West Kasai province, said at least 12 polling stations had been torched in the provincial capital, Kananga, after residents said they had found ballot papers already marked in favour of Kabila.
"I saw them, other observers saw them, journalists saw them, they exist," he stated, adding delays meant voting was continuing late into the night.
Highlighting the risk of the vote polarising the nation, Kazadi Nyembwe, a senior figure in Kabila's PPRD party, said its supporters had been intimidated in opposition strongholds, especially the Kasai provinces.
"Things have not gone properly. PPRD supporters weren't even allowed to go into (polling stations) unless they agreed to voted for Tshisekedi," he told Reuters late on Sunday.
Congo's first post-war election was held in 2006, drawing a line under years of war and chaos and paving the way for renewed investor interest in a country rich in copper, cobalt, gold and other minerals.
That vote was largely seen as free and fair.
Al Jazeera's Azad Essa contributed reporting from Goma in the Democratic Republic of Congo. Follow him on Twitter for the latest updates: @azadessa