US car giant General Motors has agreed to pay $1.5m to victims of South Africa's apartheid government after it was sued for its role in propping up the segregationist regime.

General Motors offered a settlement in the form of $1.5m worth of shares in the company nearly a decade after the human rights group Khulumani filed a US class action lawsuit against more than 20 companies for their role in abetting gross human rights violations and aid for the white-minority state.

Out of the 20, only four have not settled. They include Ford, Daimler, German defence group Rheinmetall and computer giant IBM.

"GM want to carry on with their business in South Africa and want to settle their scores and maintain good relations with the country's people," said Khulumani's Shirley Gunn, who was detained and tortured by the apartheid regime.

"But we are very grateful and can seriously start to redress the legacy of apartheid."

General Motors, which declared bankruptcy in 2009, said the settlement would be paid by a trust.

The company, however, insisted it had "adamantly opposed" apartheid and that the settlement offer did not constitute acknowledgment of any wrongdoing.

Khulumani's lawyer, Charles Abrahams, said that while part of the payment would go to the 25 plaintiffs some of the money would be will be redirected towards the legal fight against the four remaining companies in the suit.

"The fact that GM has made a without-prejudice offer to our clients clearly indicates that they acknowledge liability of some sort," Abrahams told Reuters.

"That is a significant step in corporate accountability and we hope it will stand us in good stead with our class action against Ford, Daimler, Rheinmetall and IBM."

The apartheid regime was guilty of thousands of human rights violations as well as extrajudicial killings and incarcerations of activists such as Steve Biko who died in prison in 1977 and Nelson Mandela who became South Africa's black president after serving 27 years in jail.