There was a pretty high level of cooperation between South Africa and Israel on their suspected nuclear programs. This cooperation even extends to a suspected joint nuclear test in 1979.
A Russian military satelite in 1979 detected a bright flash over the Indian Ocean, and suspected a South African nuclear test was the culprit. They informed the US, where President Carter initiated a commission to make a finding as to whether this was a nuclear test or not. Unfortunately, there was not enough information gathered to make a solid finding.
Years later, it was learned of the presence of Israeli officials in South Africa at the time of the test, and it is now beleived that the test was a joint effort by the South Africans and the Israrelis. Other levels of cooperation between the two countries on nuclear issues is unclear.