BEIRUT (Reuters) - Saudi Arabia s Gulf Affairs Minister Thamer al-Sabhan said the personal security detail of Lebanese prime minister Saad al-Hariri, who resigned on Saturday, had  confirmed information  of a plot to kill him.  Speaking in an interview on Future, an Arabic television channel owned by Hariri, he said Hariri was in Riyadh, adding there were  security threats to the prime minister and the kingdom is keen on his safety .  