At least 250 opponents of apartheid may have been murdered during the 1980s by agents of the South African regime who laced their clothing with poison, according to the most detailed account yet given of an attempt to assassinate a religious leader.

At least 250 opponents of apartheid may have been murdered during the 1980s by agents of the South African regime who laced their clothing with poison, according to the most detailed account yet given of an attempt to assassinate a religious leader.

In what became known as the case of the poisoned underpants, two doctors have described how the Reverend Frank Chikane, who now heads the office of President Thabo Mbeki, almost died in 1989 after a special South African military unit slipped a highly toxic substance into his suitcase before he left for a trip to New York.

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Mr Chikane, who is not named in the report in The Lancet but is described as "currently a senior policy adviser in the office of the President of South Africa", collapsed and had to be admitted to hospital four times after wearing clothing taken from his suitcase. At one point he stopped breathing and had to be resuscitated.

The authors have been forced to wait a decade to publish their account to avoid prejudicing a criminal investigation into the assassination attempt in South Africa, which revealed that organophosphate, a nerve agent that can kill in tiny quantities, was put into his suitcase before he left South Africa.

The report says that Mr Chikane claimed the South African Civil Corporation Bureau, which masterminded the killing of apartheid opponents in the late 1980s, might have murdered more than 500 people, half of them by poisoning.