Zimbabwe's president Robert Mugabe has been stripped of his knighthood.

The Queen approved the annulment of the honour - awarded in 1994 - on the recommendation of Foreign Secretary David Miliband.

A Foreign Office spokesman said: "This action has been taken as a mark of revulsion at the abuse of human rights and abject disregard for the democratic process in Zimbabwe over which President Mugabe has presided."

The move comes as international pressure grows on Mr Mugabe to postpone Friday's run-off election.

Meanwhile, Nelson Mandela has also broken his silence over the crisis.

The former South African president condemned the "tragic failure of leadership" in the country at a dinner to celebrate his 90th birthday next month.

He said: "The world remains beset by so much human suffering, poverty and deprivation. It is in your hands to make our world a better one for all, especially the poor, vulnerable and marginalised.

"We look back at much human progress, but we sadly note so much failing as well.

"We have seen the outbreak of violence against fellow Africans in our own country and the tragic failure of leadership in our neighbouring Zimbabwe.

"It is within this context that we should also see the plight of those affected by HIV and Aids. It is now in the hands of your generations to help rid the world of such suffering."

Zimbabwean opposition leader Morgan Tsvangirai pulled out of the race as violence against his supporters intensified.

Mr Tsvangirai is now back in the Dutch embassy in Harare where he has been seeking refuge since he decided to withdraw from the election on Sunday.

He returned to the building after giving a brief news conference from his home.

Mr Tsvangirai earlier said the African Union, backed by the United Nations, should lead a transitional process in Zimbabwe.

His comments followed an emergency meeting of Southern African leaders to discuss the political crisis in Zimbabwe.

"I am asking the AU and SADC (Southern African Development Community) to lead an expanded initiative supported by the UN to manage what I will call a transitional process," he said.

He has pulled out of the presidential election run-off on Friday as scores of people have been killed and thousands beaten and terrorised for opposing the regime of Robert Mugabe.

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