The ringleader of a white supremacist plot to assassinate Nelson Mandela and drive black people out of South Africa has been sentenced to 35 years in jail.

Former university lecturer Mike du Toit was convicted last year of treason for his leadership role in the plot, after a trial lasting nine years.

Twenty other members of his white supremacist militia Boeremag were also jailed for between five and 35 years.

In 2002 it attempted to overthrow the governing African National Congress.

In July 2012 Du Toit, a history lecturer with a master's degree in philosophy, was convicted of being behind nine bombings in Johannesburg's Soweto township in 2002, killing one person.

He was also found guilty of authoring a blueprint for revolution intended to evict black people from most of South Africa and establish a racially "pure" nation by killing anyone who got in the way.

Du Toit was the first person to be convicted of treason in South Africa since white minority rule ended in 1994.

Mr Mandela spent 27 years in prison for his fight against apartheid before becoming the country's first democratically elected president in 1994.

Gasps of disbelief

Handing down sentence, Judge Eben Jordaan said there would have been bloodshed and chaos in South Africa if the Boeremag plot had succeeded.

Mr Mandela would have been killed by a landmine planted by the group's bomb squad if he had travelled by road, rather than by helicopter, to open a school in the northern Limpopo province, the South African Press Association (Sapa) quotes the judge as saying.

The bombers had also planned to detonate five large car bombs in the centres of Pretoria and Johannesburg when they were caught, it reports.

Analysts say that while race relations in South Africa are still an issue, white supremacist groups like Boeremag - which means Afrikaner Power in Afrikaans - have very little support.

In December 2012, police arrested four right-wing extremists suspected of planning to bomb the ANC national conference, attended by President Jacob Zuma and other top officials.

There were gasps of disbelief on Tuesday from the families of those convicted - some relatives started sobbing when the judge handed down the sentences, media reports said.

Nearly 200 people gave evidence for the state - including police informants within Boeremag - and the accumulation of their evidence is one reason why the trial took so long, correspondents say.

Two of Du Toit's co-conspirators, Herman van Rooyen and Rudi Gouws - who both escaped from custody and were rearrested - were given longer sentences for their roles in planting bombs and plotting to kill Mr Mandela, local media reported.

Judge Jordaan took into consideration that almost half of the accused have spent up to 11 years in jail, which means some of them were able to walk out of court on Tuesday as free men.

Correspondents say that there is hope that the sentences have brought an end to one of the longest-running and most expensive trials in South African legal history, even though there is a possibility that some will appeal.