Counting was due to begin shortly after polls began closing in the knife-edge race between Mugabe and his longtime political rival Morgan Tsvangirai.
The 89-year-old Mugabe is Africa’s oldest leader and is running for office for the seventh and perhaps final time, but his rivals hope the election will usher in a new era for the southern African nation.
At one station in central Harare translucent boxes with grey covers were sealed with yellow cable ties, while at others voters already queueing were being given a chance to cast their ballots.
Organisers had reported high turnout across the country for the first election since the violent polls of 2008 which ended in an uneasy power-sharing government.
At many stations voters started queuing before sunrise in the winter cold and long before they opened. The lines continued well into the evening, with many marking their ballots by candle light.
“I am sure people will vote freely and fairly, there is no pressure being exerted on anyone,” Mugabe said as he cast his vote in a Harare suburb.
The one-time teacher came to prominence as a hero of Africa’s liberation movement, guiding Zimbabwe to independence from Britain and white minority rule.
But his military-backed rule has been marked by a series of violent crackdowns, economic crises and suspect elections that have brought international sanctions and made him a pariah in the West.
Mugabe said Tuesday he would step down if Tsvangirai — his reluctant coalition partner for the past four years — is the victor.
“If you lose you must surrender,” he said, insisting: “We have done no cheating.”
But Tsvangirai, the current prime minister, said that promise should be taken “with a pinch of salt.”
Tsvangirai won the first round of voting in 2008, but was forced out of the race after 200 of his supporters were killed and thousands more injured in suspected state-backed attacks.
Voting this year has been calm, but the 61-year-old former union boss has repeatedly voiced concerns that the election is being rigged.
Tsvangirai’s party on Wednesday listed a battery of alleged irregularities including thousands of voters finding their names missing from the electoral roll.
“Thousands and thousands of people are being disenfranchised,” said Finance Minister Tendai Biti, a senior member of Tsvangirai’s Movement for Democratic Change.
Biti, speaking after a meeting with the electoral commission, added: “They are admitting that there’s still two million people who are dead on the voters’ roll, but they said ‘because they’re dead, they can’t vote’.”
The MDC had on Tuesday handed what it claimed was documentary evidence of duplicate and ghost voters to observers from the Southern African Development Community (SADC).
With no Western groups allowed to cover the presidential and parliamentary poll, SADC’s account of events will be closely watched.
Still, Tsvangirai cut a confident figure as he cast his own ballot, predicting his MDC would win “quite resoundingly.”
“This is a very historic moment for all of us,” he said. It is the time to “complete the change.”
Turnout appeared to be brisk in the urban areas where Tsvangirai has enjoyed his strongest support, and which he must retain to stand any chance of victory.
Voters stood in the cold for hours to cast their ballot.
First-time voter Gamuchirai, dressed in red track suit pants and a pink sports jacket, pulled out her left hand from her pockets to proudly show off her index finger that had been dipped in purple ink for the ballot.
“A good Zimbabwe, that’s all we want, where there is electricity, jobs and water. I hope it will come,” said the 20-year-old college student.
Zimbabwe Electoral Commission boss Rita Makarau said there were isolated voting problems but reported “a high voter turnout generally at all polling stations.”
But some analysts cautioned against interpreting that as a sign Tsvangirai would sweep the election.
“This election is going to be decided in the rural areas,” where two thirds of Zimbabweans live and where Mugabe enjoys strong support, said Michael Bratton, founder of polling organisation Afrobarometer.
“That margin is exaggerated by the fact that voter registration has been very heavy in those areas and been suppressed in the towns.”
“There is a very real possibility that ZANU-PF could marshall enough votes to win the presidential election.”
Some 6.4 million people, around half of the population, are eligible to vote and a candidate needs 50 percent of the vote to avoid a run-off.
The sharp tongued Mugabe has focused his campaign on bashing homosexuals and on promises to widen the redistribution of wealth to poor black Zimbabweans.
Amid recovery from an economic crisis that saw mass unemployment and galloping inflation, Mugabe loyalists insist their hero is “tried and tested.”
Tsvangirai hopes his plans to lure back foreign investors, create a million jobs in five years and improve public services will deliver a long-awaited victory.
The final results are expected with five days.