JOHANNESBURG, Aug. 5 (Xinhuanet) -- A South African citizen has been arrested in Mexico for alleged involvement in al-Qaeda-linked terrorist activities, South African media reported on Thursday, prompting further speculation about al-Qaeda presence in the country. The man, so far unidentified, was carrying a South African passport and a mobile phone that had been used to make calls to South Africa when he was nabbed in Mexico near the US border on Tuesday, said local newspaper Thisday. However, the South African government has yet confirmed if the man is genuine South African citizen or foreign national holding South African travel...