Polls have closed in Zimbabwe's elections with President Robert Mugabe facing the toughest challenge to his 33-year grip on power.
A few polling stations were prepared to stay open into the night to accommodate all voters who were in line by 7pm, election officials said.
Vote counting is expected to begin on Wednesday night and final results are expected by Monday.
Rita Makarau, the head of the election commission, told a news conference in the capital Harare that those who were not able to vote would be given the opportunity to cast their ballots.
"If people are still in the queues, they will be allowed to complete their vote," she said.
"Polling stations were still clearing queues by 18h00 local time and we have allowed voting to continue until midnight."
Makarau reported what she called "a few minor logistical problems" where voting started slowly, and appealed to people to put forward any evidence of voting irregularities.
She also confirmed that the Zimbabwe Election Commission had received reports of 20 fake voter registration slips in Hatfield, a high density suburb in the capital Harare, and the matter was being investigated, reported Al Jazeera's correspondent Azad Essa.
Zimbabweans voted in large numbers despite concerns about the credibility of the electoral process, and the vote was relatively peaceful compared to disputed and violent polls in 2008.
Thousands of voters lined up in Harare's populous Mbare township but by the evening all the voters had been accommodated, said polling officials. "It's a tremendous turnout," said Magodelyo Yeukai, Mbare presiding officer.
|Al Jazeera's Mohammed Adow reports from Zimbabwe
The real tussle is between Mugabe and Morgan Tsvangirai, the leader of the Movement for Democratic Change who is also prime minister.
Tsvangirai, 61, predicted his party would win "quite resoundingly". "This is a very historic moment for all of us," he said.
Tsvangirai narrowly beat Mugabe in the last elections in 2008 but boycotted a presidential run-off vote to protest widespread violence against his Movement for Democratic Change party.
A third candidate, Welshman Ncube, leader of a breakaway faction of Tsvangirai's party, MDC-N, is likely to draw votes from Tsvangirai in the western Matabeleland provinces.
Polling officials and party agents brought blankets to polling stations so that they could sleep next to the polling boxes to make sure they were not tampered with.
Some election observers noted cases of registered voters being turned away from the polls. There have been worries about oversights in the hasty preparations for the vote, as well as fears of alleged vote-rigging of the kind that occurred in past elections.
Tendai Biti, the third-ranking official in the opposition and finance minister, reported alleged irregularities across several districts, including changes to voters' lists and ballot papers.
But "we are encouraged by the high turnout. We remain confident in spite of all these challenges," Biti said late on Wednesday.
The head of African Union observer mission, former Nigerian President Olusegun Obasanjo said reports of irregularities "will be investigated but have not yet been substantiated."
Activists believe a big turnout is likely to favour Tsvangirai, by blunting the impact of any manipulation of voters' rolls. Mugabe, who barred Western observer missions, says allegations of vote-rigging amount to mudslinging by opponents.