A group calling themselves the Boer Nation Warriors (Boerevolk-Krygers) have claimed responsibility for the recent bomb blasts in Soweto and Bronkhorstspruit, an Afrikaans daily newspaper reported on Monday.
According to reports, the group sent letters, which carried a black and red logo, to several media organisations via email and signed them off only as the "Warriors of the Boer Nation".
The origins and credibility of the letters would be investigated by the police.
In the letters the Boer Nation Warriors said the bomb blasts were the "beginning of the end of the African National Congress government".
They accepted full responsibility for the blasts and said they marked the end of the oppression of the Boer nation.
The rightwing group also demanded that 35 of their compatriots be released from prison, just as President Thabo Mbeki had pardoned 35 prisoners earlier in the year.
They said the 18 members of the so-called Boeremag must be part of the 35 released.
The Warriors threatened that the ANC would be held accountable and suffer consequences before and during the "false and worldly festive season" if their demands were not met.
The letter and its contents came to light after the police over the weekend released pictures of six men they wanted to question in connection with rightwing activities, including the Soweto and Bronkhorstspruit blasts.
It was also the first time that a group had claimed responsibility for the bomb blasts, which killed a woman, wounded her husband and caused millions of rands damage to railway lines around Soweto, as well as a Buddhist temple in Bronkhorstspruit.
In another development in the ongoing investigation into rightwing activities, police were reportedly looking at the possibility that a young white female corporal who was arrested at the Potchefstroom army base in the North West, could be linked to rightwing groups.
The corporal, who was arrested last week according to reports, allegedly had stolen ammunition and computer software in her possession.
She was reportedly arrested by the military police at a control point last week.
National Police Commissioner Jackie Selebi said police were investigating whether the corporal was in any way connected to rightwing organisations.
Selebi warned people harbouring the six suspects whose pictures were released at the weekend that they were committing a crime.
"The purpose of publicising the pictures was so that people who are harbouring those suspects and those who may come across them should inform the police," he said.
Selebi said it was too early to release any information on progress in finding the six. "We know we will get numerous calls, people saying this and that and others making prank calls," he said.
The SA Police Services also moved on Sunday to clarify reports on the manhunt for six rightwing coup suspects, emphasising that they were not being sought specifically for last month's bombings.
Selebi's spokesperson, Director Sally de Beer, said no warrants of arrest had yet been issued in connection with the Soweto blasts which killed one person.
The six were being sought as part of the continuing investigation into the high treason, terrorism and sabotage case for which 18 suspects have already been arrested for planning to overthrow the government violently.
"No warrants of arrest have been issued for the Soweto bombings. At this stage police believe that four of the six men could be of assistance in their investigation of the Soweto bombings and would like to interview them on the incident," she said.
Three of the six men being sought are the sons of a medical doctor from Mokopane in Limpopo, Dr Johan "Lets" Pretorius, who was arrested recently after police confiscated a truck containing medical equipment and weaponry.
Pretorius is in custody with 17 others, including the alleged leader of the Boeremag, Tom Vorster, who was arrested a week ago. They are to stand trial in the Pretoria High Court on charges of treason and terrorism in May next year.
The other men being sought by the police are Herman van Rooyen, 28, Rudie Gouws, 25 and Herman Visagie, 63, all three are from Bela-Bela, Warmbaths.
The three brothers are Kobus Pretorius, 29, Wilhelm Pretorius, 25 and Johan Pretorius.