Pretoria — Five of the Boeremag accused were found guilty on Friday of conspiring to murder former president Nelson Mandela.
Nineteen of the 20 accused have already been found guilty of high treason.
Judge Eben Jordaan found Boeremag bombers Herman van Rooyen, Rudi Gouws, and brothers Johan, Kobus, and Wilhelm Pretorius guilty of conspiring to murder Mandela with a home-made bomb in October 2002.
The five were also found guilty of culpable homicide resulting from the death of Claudia Mokone in Soweto in October 2002.
Mokone died when a piece if steel dislodged by a Boeremag bomb on a railway line flew 400m through the air, penetrated the roof of her shack and struck her head.
The judge said the State had not proved that the accused murdered Mokone.
There were no houses visible near the railway line and the bomb went off at midnight when there were few people around.
Anyone planting a bomb would, however, foresee that someone could be killed.
The other 15 accused were acquitted on the murder charge.
Jordaan said they could not be held responsible for the negligent conduct of the five bombers.
He accepted the evidence of co-conspirator Deon Crous that he and the five bombers had decided to murder Mandela on the spur of the moment.
This was after they saw a newspaper report that he would open a school in Bolobedu, near Tzaneen.
They believed Mandela's death would result in blacks attacking whites in the country, leading to whites supporting the Boeremag's cause to take over government.
Wilhelm Pretorius' war diary, in language riddled with racist remarks, described in detail the attempt on Mandela's life.
According to the diary, they had immediately decided "k...., here we come" on seeing the newspaper report, because it would be the "sign" they had been waiting for if Mandela died.
Van Rooyen and brothers Johan and Wilhelm had travelled to Bolobedu with a home-made bomb intending to blow up the school.
The bomb was eventually put in a ditch next to the road they hoped Mandela would use.
Fishing line was strung across the road and two of them hid in the bushes to set off the bomb when they saw Mandela's car.
They had prayed that if they were destined to kill Mandela, the weather would not allow him to travel by helicopter that day.
According to the diary, they realised their plan had been thwarted when they heard a helicopter.
"We knew then that the k... can still be allowed to breathe," (die k... kan maar nog asem haal)," he said.
Van Rooyen later dismantled the bomb.
He and Wilhelm Pretorius hid in the bushes until dark, when Johan Pretorius came to pick them up.
The diary stated that God had protected them that day because they were not caught, despite being confronted by a "traffic cop" and a policeman.
Pretorius was dressed in an army uniform and managed to get rid of the policeman by assuring him they were busy with an "exercise".
The next entry in the diary was headed "Soweto, those bastards" and stated that the group would go ahead with bombing targets in Soweto because they had not been able to kill Mandela.
Sentencing will most likely be concluded on Monday, when judgment is expected against the last accused, Kobus Pretorius.