Electoral challenge

Mugabe is facing the sternest challenge to his 28-year rule after losing a first round vote in March to Morgan Tsvangirai, who leads the Movement for Democratic Change (MDC).

Zimbabwe's electoral commission ruled that although Tsvangirai won the first round of the presidential vote, he did not secure the majority necessary to prevent a run-off against Mugabe.

Tsvangirai arrived in Zimbabwe on Saturday, after spending six weeks lobbying regional leaders to put pressure on Mugabe.

Tsvangirai has returned to Zimbabwe after six weeks outside the country [AFP]

He had postponed his return several times, alleging Zanu-PF supporters were planning to assassinate him.

In a speech at the funeral of Tonderai Ndira, one of at least 40 activists the opposition say have been murdered in the last two months, Tsvangirai promised not to betray his memory.

"This [murder] is clear testimony of the callousness of this regime and the extent to which they are prepared to go in order to stay in power without the support of the people," he said.

"They can kill us, they can maim us, but on June 27 we are going to vote this man out. We will not betray the life of Tonderai."

The opposition claims that Zanu-PF supporters have waged a campaign of violence and intimidation against opposition supporters in order to influence the outcome of the run-off vote.

Human rights groups and the United Nations have said the attacks are being directed at followers of MDC. Zanu-PF has denied the allegations.

Tsvangirai has rejected the idea of a coalition government with Mugabe and has called for regional peacekeepers and election monitors from the Southern African Development Community (SADC) to be deployed by June 1.

No Western monitors were allowed to oversee the first ballot and teams from SADC and the African Union were widely criticised for giving it a largely clean bill of health.