ROBERT MUGABE has put his security forces on alert to crush disturbances if, as expected, he wins this weekend's presidential election and adds another five years to the 28 he has already been in power.

It has been clear for months that 84-year-old Mugabe intends to win, by fair means or foul, in order to preside over a state with the world's highest inflation rate - at more than 100,000% - and whose citizens have the world's lowest life expectancy - just 34 years for women.

If the voting were truly free and fair in a genuine democracy, Mugabe's reign would be over. But liberty and legitimacy are not parts of modern Zimbabwe's reality. Mugabe, interested only in retaining power and avoiding prosecution for human rights abuses, has destroyed the economic, education and healthcare systems, turning a once-prosperous country into a forlorn despotism scarred by hunger and bitterness.

Human rights organisations and the political opposition allege overwhelming evidence of manipulation of the polls through ballot fraud, tampering with the voters' roll, gerrymandering of constituency boundaries and insufficient polling stations in urban areas where Mugabe's opponents have most support.

More than nine million paper ballots have been printed for six million registered voters. Some 3.5m Zimbabweans who have fled the country cannot vote, but 600,000 ballots have been printed for 20,000 Zimbabwean diplomats and soldiers abroad.

Campaign posters showing Mugabe wearing a military shirt and holding a clenched fist aloft reflect his hardline politics and have reminded voters about the tough military and police officers who have helped keep him in power since independence in 1980.

"For Mugabe, political thuggery is always an option," said Morgan Tsvangirai, leader of the opposition Movement for Democratic Change (MDC) and one of two people on the ballot against the incumbent president this weekend. In response to Mugabe's "Vote for the Fist" campaign, the MDC asserted in independent weekly newspaper adverts: "The (independence) war is over. We cannot feed people with clenched fists."

Mugabe's other challenger, his former finance minister Simba Makoni, has been telling rallies: "Don't vote for the fist. The fist has become a hammer smashing the country."

Zimbabwe's armed forces chief, General Constantine Chiwenga, a close ally of Mugabe since the years of the struggle against white minority rule, has warned that the military will use its fist and reject any result that favours "sellouts and agents of the West".

Mugaberegularly describes Makoni as a "sellout", a pejorative term of abuse in the tradition of African liberation politics, and Tsvangirai as a tool of Britain and other Western states.

Mugabe has been telling rallies that his opponents will not rule in his lifetime. He told cheering supporters of his ruling Zanu-PF party in Bulawayo: "You can vote for them Tsvangirai, the MDC and Makoni, but that will be a wasted vote. You will be cheating yourself as there is no way we can allow them to rule this country.

"We have to protect our heritage. The MDC will not rule this country. It will never, ever happen. We will not yield." Pointing to the clenched fist symbol, Mugabe said: "We have the fists, and we can box."

Moving to the other side of Zimbabwe, Mugabe told a rally last Thursday in the eastern Highlands, a stronghold of Mugabe's pre-independence guerrilla army, that his opponents should forget about protesting if they emerge as losers in the contest.

"Just dare try it," said Mugabe. "We don't play around while you try to please your British allies."

But there is clearly anxiety within Harare's corridors of power that there might be anti-government riots, similar to those that rocked Kenya after its disputed December elections, if Mugabe again wins what many see as a rigged election for the fourth time since 2000.

"The army, police and other key security agencies have been put on alert because the government fears that there could be an eruption of protests and violence after the elections," a senior government official told the weekly Zimbabwe Independent, virtually the only surviving critical media voice following sustained government crackdowns on independent newspapers and broadcasters.

Opposition and civil society organisations have condemned what they see as thinly veiled threats of a military coup by diehard generals if the vote does not go Mugabe's way.

"My assessment is that Makoni will come third in the elections," said Eldred Masunungure, a professor of political science at the University of Zimbabwe. "The real race is between Mugabe and Tsvangirai.

But these are academicdiscussions and speculation as the president will take steps to prevent his electoral ambitions going awry.

"Mugabe will not allow himself to go through all this pain for no purpose. That explains his insistence that no opposition leader or party will win the elections, and he knows he has played his cards well."