The British Guardian overnight published declassified South African documents, which it said reveal that Israel offered to sell nuclear warheads to the apartheid regime, DPA reported.
The Guardian says the documents provide the first ever official documentary evidence that Israel actually possesses nuclear weapons.
Israel has long followed a policy of "nuclear ambiguity," meaning it neither confirms nor denies that it has the atom bomb.
The policy is aimed at enjoying the deterrence of a bomb, without the likely consequences of international inspections or even sanctions or a regional arms race.
The documents published in the Guardian include the "top secret" minutes of meetings between senior officials from the two countries in 1975 and show that South Africa's defence minister, PW Botha, asked for the warheads, while Shimon Peres, then Israel's defence minister and now its president, responded by offering them "in three sizes."
Peres' signature can be seen under a letter dating from 1975.
The papers were uncovered by an American academic, Sasha Polakow- Suransky, in research for a book on the close relationship between the two countries.
Peres' office told the German Press Agency dpa that a reaction would be forthcoming.