South Africa shot off a couple nukes that were never really reported
Supposably South Africa had a joint nuclear weapons development program with Israel. Urban legend has it that South Africa did two atmospheric tests in the Southern Indian Ocean. An old Vela satellite detected one of the tests. The Vela saw the characteristic double pulse of a nuclear explosion (what's the physics behind that?). At the time, people didn't know what to think about it. The Vela was such as old satellite that people originally thought it was a glitch. Then the news filtered through that it was a South African nuke and by implication an Israeli one as well. Acknowledging that created more problems than solutions so people just stayed quiet about it.
Gary