Hundreds of thousands of dollars' worth of counterfeit money has been printed in Johannesburg and used to help finance the Mozambican rebels challenging the Marxist government of President Samora Machel, South African Foreign Minister R.F. (Pik) Botha said at a press conference in Pretoria today.

Botha also disclosed that the forgery gang was connected with a massive smuggling racket in ivory, emeralds, diamonds and prawns -- a prized delicacy -- which were sold to buy arms for the rebels.

The smuggled goods were flown from Mozambique to South Africa and other African countries, and one of the aircraft being used has an American registration, the foreign minister said.

Jorge Correia, spokesman for the Mozambique National Resistance, dismissed the charges in a telephone interview from Lisbon with United Press International. "The South African foreign minister once again tries an invention to discredit the real nationalistic movement," Correia said.

It was the first time the Pretoria government has admitted that the Mozambique rebels are continuing to receive aid from South African territory in violation of the Nkomati Accord which it signed with Machel one year ago today.

Botha, who has just returned from an urgent mission to Maputo to shore up the Nkomati Accord in the face of growing Mozambican disillusionment with it, strenuously denied that his government was responsible for the continued aid to the rebels.

The foreign minister said the real supporters of the rebel movement, known by its Portuguese abbreviation, Renamo, were "an international web of bankers, financiers and businessmen" with interests in Africa, Latin America and Europe.

These conspirators, who Botha said were as hostile to the South African government as they were to Machel, wanted "to turn Mozambique into their own private economic preserve," he charged.

He would not disclose who they were but said he had shared with Washington the information his government had gathered about them.

While Botha did not identify the conspirators, it was believed here that many might be Portuguese. There are an estimated 700,000 Portuguese living in South Africa, many of them refugees from Mozambique, a former Portuguese colony.

Citing steps South Africa has taken to stop the flow of aid from its territory, Botha said low-level radar had been installed along the border to check for clandestine flights. This network had picked up the signals of three mysterious flights since it became operational only eight days ago. He also said some pro-Renamo Mozambicans had joined South African military units based near the border, and said they would either be stationed elsewhere or removed from the defense force altogether.

Botha said police had uncovered a Renamo-connected "criminal gang" in Johannesburg that had printed large quantities of counterfeit $100 and South African 50-rand (worth about $25) banknotes, as well as a number of anti-Machel propaganda pamphlets.

Some of the forgers had been arrested and would appear in court soon, Botha said. He did not say how many were arrested or identify them. He added that two had escaped and fled to a European country that he did not name.

In an apparent attempt to balance the admissions he was making, the foreign minister said he had lodged a complaint with the Mozambican government about its "derogatory" statements on South Africa's segregationist system called apartheid.

"While we appeal to Renamo to lay down its arms, they continue to give psychological, diplomatic and moral support to the African National Congress," Botha said, referring to the main underground movement fighting to overthrow apartheid.

The anniversary of the accord, which was acclaimed on both sides as a diplomatic triumph when it was signed, is passing without much celebration on either side.

Mozambique suffered a loss of face in black Africa by entering into a formal treaty with the apartheid government, and by appearing to abandon the African National Congress.

Despite the signing of the agreement, rebel activity has increased in Mozambique.

For its part, South Africa has succeeded in having the African National Congress effectively expelled by Mozambique, but has not won the hoped-for improvement in relations with black African countries.