South African prosecutors have begun outlining their case against two men accused of being part of a global nuclear weapons smuggling ring.
The two men will contest the charges, their lawyers say
Gerhard Wisser, 66, and Daniel Geiges, 65, are accused of importing and exporting equipment capable of being used in uranium enrichment.
Their lawyers say the two men - both engineers - intend to plead innocent.
South Africa links last week's arrests to Libya's nuclear efforts, which Tripoli agreed to abandon last year.
The case came as South Africa agreed to co-operate with the International Atomic Energy Agency (IAEA) in its investigation of the activities of the Pakistani scientist, AQ Khan.
Dr Khan last year confessed to leaking nuclear secrets illegally to countries including Libya, Iran and North Korea.
IAEA's head Mohamed ElBaradei said on Tuesday the South African investigation was providing good information about the Libyan and Iranian nuclear programmes.
Mr Meyer withdrew a bail application shortly before charges were dropped
Mr ElBaradei's comments came after South African prosecutors said last week equipment seized in the country exactly matched that in a video of Dr Khan's laboratory in Pakistan.
"This case must rank as one of the most serious in the world," South African prosecutor Chris MacAdam told the court in Vanderbiljpark, outside Johannesburg, according to Reuters news agency.
Mr Wisser of Germany and his Swiss colleague, Mr Geiges, have been living permanently in South Africa.
A third man - who was arrested last week on similar charges - decided to turn state witness to help the investigation, Mr MacAdam said.
He said the charges against the third men, South African engineer Johan Meyer, 53, were subsequently dropped.