Gerhard Wisser, 66, and Daniel Geiges, 65, both living permanently in South Africa, appeared on four counts of contravening the Nuclear Energy Act and a law banning the proliferation of weapons of mass destruction.

Their arrests follow that of a South African businessman over his alleged links to a nuclear smuggling network thought to be linked to Pakistani scientist Abdul Qadeer Khan and aimed at helping Libya develop an atomic weapons programme.

The two Germans "unlawfully and intentionally imported, held in transit and exported goods which may contribute to the design, development, production, deployment, maintenance or use of weapons of mass destruction without a permit," the charge sheet said.

The three other charges relate to the possession, manufacture and export of equipment for the enrichment of uranium.

Last Thursday, South African businessman Johan Meyer, 53, was arrested for his alleged links to a global nuclear smuggling network and charged with possessing sensitive nuclear-related equipment and illegally importing and exporting nuclear material.

But the charges were dropped on Wednesday, and the Germans were arrested the same day, fuelling speculation that Meyer had agreed to cooperate with the state in exchange for immunity.

The case against the two Germans was postponed in the Vanderbijlpark regional court, some 80 kilometres (50 miles) south of Johannesburg, for a formal bail application on Tuesday. The two men were not asked to plead.