HARARE, Zimbabwe (AP) -- Voting concluded Wednesday in most of Zimbabwe's polling stations in elections in which Robert Mugabe, faced one of the biggest challenges 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 7 p.m. Vote counting is expected to begin Wednesday night and final results are expected by Monday.
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.
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 former opposition party of Prime Minister Morgan Tsvangirai, Mugabe's popular challenger, 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 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 favor 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.
Judge Rita Makarau, head of the official election commission, 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.
Kadhashu Makanyanya was one of those who was unable to vote after he was told his name was not on the voters' role.
"I checked on the computer during the voter inspection and it was there," he said. "I am going to the command center now to check for my name."
The Zimbabwe Election Support Network, an observer group, said it had observed potential voters with registration slips being turned away from the polls.
Bundled against the winter chill, thousands of voters stood patiently in long lines in the poor Harare township of Mbare and other areas.
Some wary voters said they would bring their own pens into the voting booth after hearing rumors that the ink in state-provided pens would disappear after several hours, enabling ballot manipulation.
Ten public buses from South Africa carrying expatriate voters from Tsvangirai's Movement for Democratic Change party were impounded at the border to Zimbabwe, said party member Gilbert Maganda.
In a telephone interview with The Associated Press, Maganda speculated that police stopped the buses in order to prevent people from voting. His allegation could not be confirmed, but security forces have used similar tactics in past elections.
Mugabe, 89, has said he would step down if he loses. Many Zimbabweans find it hard to believe that the wily politician, a former guerrilla who led the country to independence in 1980 and has the backing of the security forces, would relinquish control even if the vote doesn't go his way.
After voting in Harare's western Highfield township, Mugabe said he expected to be re-elected.
"We will have lots of things to do to get our economy back on its feet," he said.
Tsvangirai, who had been in an uneasy power-sharing arrangement with Mugabe, cast his ballot in northern Harare.
"We have come to complete the change we have always fought for," he said. "It is an emotional moment for me but I am filled with a sense of calmness."
The coalition between the two rivals was forged by regional leaders after Zimbabwe's last disputed election in 2008.
Zimbabwe's shaky government was effectively dissolved on Wednesday; Mugabe and Tsvangirai have each predicted outright victory that would avoid the formation of another coalition.
Half the population of 12.9 million is eligible to vote. The state election body has said administrative, logistical and funding problems hindered voting arrangements, but said the problems have been fixed at the more than 9,000 polling stations nationwide.