Robert Mugabe has said he is heading for a "sweeping victory" in the unopposed run-off election to choose Zimbabwe's president.

Mr Mugabe said returns suggested that he had won all constituencies in the opposition stronghold of Harare.

He was the only candidate after the opposition boycotted the vote amid reports of violence and intimidation.

African observers of the poll called on Sunday for fresh elections to be held, saying the vote was not free or fair.

Crucial reaction

"The returns show that we are winning convincingly, that we have won in all the 26 constituencies in Harare, an MDC stronghold where we won in only one constituency in March. That is the trend," Mr Mugabe said in footage broadcast on state television.

It is thought he will be sworn in as president on Sunday, even though official results are yet to be published.

Morgan Tsvangirai, leader of the Movement for Democratic Change (MDC), announced he was pulling out of the election last Sunday.

But his name remained on ballot papers after Zimbabwe's electoral authorities refused to accept his decision.

The BBC's Peter Biles, in Johannesburg, says the expectation is that Mr Mugabe will want to declare victory before leaving for a summit of African Union leaders that opens in Egypt on Monday.

The reaction of Zimbabwe's neighbours in southern Africa will be crucial, our correspondent says.

An observer team from the Pan-African Parliament on Sunday called on regional grouping Sadc and the African Union to facilitate talks between the government and opposition.