Zimbabweans began voting on Friday in an election which was virtually certain to end in victory for President Robert Mugabe but dismissed by the opposition as meaningless after it boycotted the poll.

Despite predictions in state media of a "massive" turnout, the amount of voters queuing to cast their ballots when polling stations opened at 7am (0500 GMT) represented only a fraction of those seen in the first round 13 weeks ago when opposition leader Morgan Tsvangirai emerged as the winner.

One of the first to vote was Danger Zvembabvu, a 50-year-old veteran of Zimbabwe's 1970s liberation war, but he cut a lonely figure as he waited for election officers to open the doors of a station in central Harare.

"I have been queuing since 3am but I was the only one," he told AFP.

"I am excited. This is an exercise I feel I have to be part of because I love my country."

Tsvangirai however said the election, which he decided to boycott after a wave of deadly attacks against his supporters, was a source of shame.

"Today is not an election. Today is a shameful humiliation, another tragic day in our nation's history," Tsvangirai wrote in a letter to party supporters.

"Today's results will be meaningless because they do not reflect the will of the people of Zimbabwe. Today's results reflect only the fear of the people of Zimbabwe."

While Tsvangirai says Africa's oldest leader must accept his time is up, the 84-year-old Mugabe believes the outcome will give him a mandate to continue governing as he sees fit.

A raft of international and regional leaders meanwhile have urged Mugabe to shelve the election, arguing that spiralling violence has precluded the possibility of a free and fair ballot taking place.

A total of 5.9 million Zimbabweans will theoretically be entitled to cast their ballot at around 9,000 polling stations over the course of 12 hours, overseen by some African but no Western monitors.

The so-called run-off election comes some 13 weeks after an initial ballot which saw Mugabe beaten into second place with 43.2 per cent against 47.9 per cent for Movement for Democratic Change (MDC) leader Tsvangirai.

The simultaneous March 29 presidential and legislative election also saw Mugabe's ZANU-PF party lose control of parliament for the first time since independence in 1980.

But the MDC says Mugabe has reversed the odds in his favour in the intervening period through a concerted campaign of violence and intimidation, claiming more than 80 of its supporters have been killed by pro-Mugabe thugs.

The violence has been particularly acute in the countryside -- the ruling party's traditional stronghold but where Mugabe did worse than expected last time round -- with the MDC saying 200,000 voters have since been displaced.

Tsvangirai's name will appear on the ballot papers with the state-run Zimbabwe electoral commission saying it is too late for him to withdraw.

Mugabe made clear in his final campaign rally that he wants to continue as president of the country which he has led uninterrupted since independence from Britain in 1980. While he would be willing to talk to the opposition, negotiations would begin only after he had won a sixth term.

"Should we emerge victorious, which I believe we will, sure we won't be arrogant, we will be magnanimous and say 'let's sit down and talk,' and talk we shall," said Mugabe.

"We will continue to rule this country in the way we believe it should be ruled."

South African President Thabo Mbeki has been leading regional efforts to forge some kind of unity government since the first round but his mediation has proved largely fruitless and Tsvangirai has urged him to step aside.

Although Mbeki has been loath to publicly criticise Mugabe, his revered predecessor Nelson Mandela has criticised a "tragic failure of leadership in our neighbouring Zimbabwe".

US President George W Bush has said Friday's polls "appear to be a sham" while UN chief Ban Ki-moon renewed his call Thursday to postpone the election "until such time when we can create fair and credible conditions."

Viewed in the first years after independence as a post-colonial success story, Zimbabwe has seen its economy collapse since Mugabe began a controversial land reform programme at the turn of the decade which saw thousands of white-owned farms expropriated by the state.

The one-time regional breadbasket now experiences shortages of even the most basic foods while inflation – officially put at 165,000 per cent but in reality many times higher still – is the highest in the world.