Its merely a story put out by Israeli propaganda machine. The Nelson Mandela Foundation has this to say about this false claim :- "In 1962 Mr Mandela received military training from Algerian freedom fighters in Morocco and from the Ethiopian Riot Battalion at Kolfe outside Addis Ababa, before returning to South Africa in July 1962." "In 2009 the Nelson Mandela Foundation's senior researcher travelled to Ethiopia and interviewed the surviving men who assisted in Mandela's training and no evidence emerged of an Israeli connection," read the statement.
Three minors arrested in Jaffa for throwing rocks at a bus; no injuries reported (Haaretz)
from the article: Mandela received weapons training from Mossad agents in Ethiopia