Four more Boeremag bombers were convicted of high treason by the High Court in Pretoria on Thursday, bringing to 19 the number of convicted members of the organisation.
Judge Eben Jordaan is expected to conclude judgment next week, nine years after the trial began.
Mokopane doctor Johan Pretorius, his brother Wilhelm, Bela Bela farming assistant Rudi Gouws, and Pretoria computer programmer Jacques Jordaan were found guilty on Thursday.
The remaining accused, herb farmer Kobus Pretorius, would hear his fate on Monday.
On Friday, Jordaan was expected to deliver a separate ruling on charges of murder and attempted murder. The latter stems from a failed attempt to kill then president Nelson Mandela with a home-made landmine near Bolobedu, Limpopo, on October 11, 2002.
Herman van Rooyen, and Johan and Wilhelm Pretorius planted the bomb on the road they hoped Mandela would use on his way to open a school in Bolobedu. Mandela arrived by helicopter instead.
The judge ruled the three, along with Kobus Pretorius and State witness Deon Crous, had all planned to murder Mandela.
The "war diary" of Wilhelm Pretorius was used as evidence in the trial. It contained a detailed plan to murder Mandela and create civil unrest and start a race war in South Africa, in preparation for a right-wing coup.
The six were also involved in a series of bomb blasts in Soweto late in October 2002. The murder charge stems from the death of Claudia Mokone. She was killed in Soweto on October 29, 2002 when a piece of railway line, dislodged by a Boeremag bomb, landed in her shack, and struck her on the head.
Dr Johan Pretorius was Boeremag leader Tom Vorster's right-hand man.
He was directly involved in attempts to plant bombs at the police air wing at Grand Central Airport, at a bridge in Port Edward, a mosque in Soweto, and at a Buddhist temple in Bronkhorstspruit.
Wilhelm, a theology student, was the Boeremag's "computer man" who helped plan and execute the bombings. He created false drivers and firearm licences on his computer.
Jordaan rejected the brothers' application to be declared prisoners of war.
Both claimed they were soldiers of the South African Boer Republic engaged in a legitimate war against the ANC government aimed at establishing an independent Boer state.
Jordaan ruled they were not fighting for the freedom of the Boer nation, but coup plotters.
Herman van Rooyen and Rudi Gouws were part of a small band of Boeremag members who continued with the plot to overthrow the government after the Boeremag leaders, including Dr Lets Pretorius, were arrested.
Even after some of their photos were published as wanted men following the first series of bomb explosions, they continued planning further terrorist acts. They set up an "explosives factory" at a farm in Limpopo, where over 1.5 tons of explosives were produced.
They were about to assemble five powerful car bombs when they were arrested in December 2002. Their intended targets included Marabastad outside Pretoria, and a taxi rank in the Pretoria city centre.
Jordaan rejected the evidence of Jacques Jordaan, who joined the Boeremag only a few days before his arrest, that he had not been aware of the coup plot.
The young computer programmer claimed he was "on a holiday" with the others, but the judge said photos of the farm clearly showed it was used as an explosives factory, not a holiday farm. Police found a gun and hand grenades in Jordaan's bed.