A US judge has ruled that lawsuits seeking financial compensation can continue against five companies accused of aiding South Africa's former apartheid system of racial segregation.

US District Judge Shira A. Scheindlin rejected requests by several countries that the lawsuits should not go ahead to protect relations between the United States and South Africa.

The judge, who issued the decision in writing on Wednesday, allowed claims made by tens of thousands of South African plaintiffs in two lawsuits in the US federal court to proceed against Germany's Daimler and Rheinmetall AG, as well as General Motors, Ford and IBM. The plaintiffs claim they were forced from their homes and resettled, arrested and imprisoned without cause and beaten and tortured by the authorities.