Zimbabwe's President Robert Mugabe, facing the toughest election battle of his 28 years in power, handed out hundreds of cars to doctors yesterday in what opponents say is a vote buying campaign.

Mr Mugabe's opponents said the veteran leader was plotting to rig tomorrow's presidential election, in which he faces old rival Morgan Tsvangirai and ruling party defector Simba Makoni.

Both accuse Mr Mugabe, 84, of wrecking what was once one of Africa's strongest economies and pauperising its people.

On national television, Mr Mugabe blamed Zimbabwe's troubles on Western sanctions imposed on him and allies to try to force reform. Mr Mugabe said the measures had harmed health care in Zimbabwe, one of the countries worst affected by HIV/AIDS.

"Our health sector (once) operated in a regional and international context that was free of the illegal sanctions which weigh us down today," President Mugabe said in a ceremony to give 450 cars to senior and middle-level doctors at government hospitals.

He promised the doctors houses within two years.

In a procedural move, Mr Mugabe told his ministers the Cabinet was dissolved ahead of the election.

"I told them that some would return to government, others will be left behind. The good performers will continue," Mr Mugabe told a rally in the town of Bindura, 70 kilometres northeast of Harare.

Mr Tsvangirai's main wing of the opposition Movement for Democratic Change (MDC) yesterday said it had more evidence of planned ballot rigging and believed Mr Mugabe was planning to declare victory with almost 60 per cent of the vote. Mr Tsvangirai, Mr Makoni and Arthur Mutambara, leader of the MDC's smaller faction, told reporters after holding talks that Mr Mugabe had put the credibility of the election in doubt.

"We believe there is a very well thought out, sophisticated and premeditated plan to steal this election from us," said Mr Makoni.

Mr Mugabe has also handed out farm equipment and public buses in what critics say is an attempt to win political favour ahead of the vote in a country where many can no longer afford even basic needs and food and fuel are in short supply.