Five members of a white supremacist group on Tuesday were sentenced to 25 years in prison for plotting to assassinate anti-apartheid hero Nelson Mandela and overthrow the democratically elected government.

The sentences were handed down by the North Gauteng High Court in Pretoria in a trial that had lasted more than 10 years, costing 36 million rands (about 3.6 million U. S. dollars) in legal costs, the most expensive trial in South Africa's legal history.

The five men, members of Boeremag, or Boer Army, were found guilty of trying to overthrow the government led by the African National Congress (ANC) and plotting to assassinate Mandela, the court ruled.

Boeremag leader Tom Vorster and four of his men -- Herman van Rooyen, Johan and Wilhelm Pretorius, and Rudi Gouws -- were each given a jail term of 25 years.

The third Pretorius brother, master bomb maker Kobus Pretorius, was sentenced to 20 years of imprisonment, of which 10 years were suspended.

Others of the 21 defendants of the group received sentences ranging from five years to 20 years.

The convicted were accused of bombing numerous targets in Johannesburg and Pretoria in a coup attempt in 2002.

They were also accused of attempting to assassinate Mandela, who was South Africa's first black president, by planting a bomb along a route he was due to travel. But the plot was thwarted when Mandela arrived by helicopter instead.

In one of the blasts in the black township of Soweto in Johannesburg, one woman was killed.

Boeremag had suggested driving all black, colored and Indian people out of the country.