The U.N. General Assembly today instructed Secretary General Kurt Waldheim to investigate U.S. reports that South Africa recently exploded a nuclear device, but African diplomats indicated they accepted the reports as true.

Nigeria's ambassador to the United Nations, B. Akporode Clark, speaking on behalf of the African group, told the General Assembly that the alleged blast has created "a fait accompli of tragic and monstrous proportions."

Clark called on the assembly to ask Waldheim to conduct an inquiry and report his findings, and the assembly approved the request without a vote. The assembly's president, Salim Ahmed Salim of Tanzania, said that if true, the atomic test by South Africa "would clearly constitute a serious threat to peace and security in Africa."

Clark said the United States, Israel, Britain, France and West Germany must share the blame "for this grave and unprecedented threat to the security of Africa." He accused those countries of nuclear cooperation with South Africa.

Clark criticized the United States for delaying disclosure of the alleged nuclear test and called this "a sad commentary on international morality."

American, British and Israeli officials promptly denied that there was any cooperation on nuclear power between them and South Africa.

The U.S. ambassador to the United Nations, Donald McHenry, told Clark after the Nigerian's statement that the United States has not supplied nuclear materials to South Africa for the past four years and was fulfilling its responsibility by pursuing its inquiry into the possibility of a nuclear explosion. McHenry added that the event remained unconfirmed.

McHenry said the United States had discontinued even peaceful nuclear programs with South Africa and would not resume them until that country signs the Nuclear Nonproliferation Treaty, which it so far has refused to do. He said the United States would cooperate with Waldheim in investigating the incident.

The Soviet news agency Tass said in a report from New York that Western countries and Israel had supplied South Africa with the technology and equipment to produce enriched uranium, which can be used to make atomic weapons. Tass accused the United States of trying to "dissociate itself from the responsibility which the Western powers bear for building South Africa's nuclear potential in the course of a number of years."

Meanwhile, other African groups reacted strongly to the reports of a South African nuclear blast.

The African National Congress, a South African opposition movement based in Zambia, demanded an urgent U.N. Security Council meeting to impose sanctions on South Africa.

The U.N. representative of the Southwest Africa People's Organization called for a more stringent arms embargo on South Africa, and said the blast was designed to undercut negotiations on Namibia (Southwest Africa) and Zimbabwe-Rhodesia.