Crisis-weary Zimbabweans vote Wednesday in a fiercely contested election dominated by Robert Mugabe's bid to extend his 33 year rule and suspicions of vote rigging.

The 89-year-old president, Africa's oldest leader, is running for election for the seventh and perhaps final time, after a series of violent crackdowns, economic crises and suspect elections.

But on the eve of the vote, Mugabe vowed to step down if he lost and claimed the army -- long the bulwark of his rule -- would also respect a victory for Morgan Tsvangirai, his perennial rival.

"If you lose you must surrender," the 89-year-old firebrand said at a rare press conference in Harare just hours before the polls open at 0500 GMT.

Tsvangirai, who was forced out of the race in 2008 after 200 of his supporters were killed, told CNN he took Mugabe's promise "with a pinch of salt."

While this year's campaign has seen little of the bloodshed that marred the 2008 election, the 61-year-old former trade union leader has raised alarm about silent manipulation

Tsvangirai's Movement for Democratic Change on Tuesday handed what they claimed was documentary evidence of plans to rig the election to observers from the Southern African Development Community (SADC).

The dossier, which was seen but could not be independently verified by AFP, listed examples of duplicate or questionable voters gleaned from a inital examination of the electoral roll.

In June, the Research and Advocacy Unit, a non-government group, said after examining an incomplete roll that it included a million dead voters or emigres, as well as over 100,000 people who were more than 100 years old.

"We have seen a lot of duplicate names in the roll, where you see somebody is registered twice, same date of birth, same physical address but with a slight difference in their ID number," junior minister Jameson Timba told AFP.

A SADC observer, who asked not to be named because he was not authorised to speak to the press, said the MDC dossier raised serious questions.

"It's not normal. If the roll had been released two weeks ago, these kind of problems would have been fixed."

Mugabe vehemently denied ever rigging the vote. "We have done no cheating, never ever."

Late Tuesday the Zimbabwe Electoral Commission was ordered to fully publish the roll by 1000 GMT Wednesday. But with the vote well underway, that leaves little time to correct problems.

Electoral commission chief, justice Rita Makarau said the delayed access to the roll had affected all parties "equally."

"It has not affected one political party, so in a way it remains unfair to all political players," she told the parties representatives on Tuesday.

Some 6.4 million people, around half of the population of 12.9 million Zimbabweans, are eligible to cast ballots at 9,670 polling stations across the country.

Either man needs 50 percent of the vote to avoid a run-off and both appear confident they can manage that feat.

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".

Credible opinion polls are rare, but according to one survey by the US-based Williams firm in March-April, Mugabe could be in for a rough ride.

In a survey of 800 Zimbabweans, 61 percent said they had a favourable view the MDC compared with 27 percent for Mugabe's ZANU-PF.

The poll showed Tsvangirai leading in seven of 10 provinces and that only 34 percent of those who voted for Mugabe in 2008 back him for president this time around.

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.

Outside the aspirants' promises voters are far more concerned first with peace, then economic growth and jobs creation.

"Jobs and peace. Those are the two things I wish for," said 38-year-old Murinda vending mobile phone spares and DVDs at a market stall in the middle class suburb of Avondale.

"My prayer is that there is peace after the elections and the economy starts functioning normally again."

Polling stations open at 7:00 am (0500 GMT) and close 12 hours later.

Final results are expected with five days.

The elections will also chose lawmakers and local government councillors.

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