"Don't kill me, don't kill me," she said, according to the man who wanted to remain anonymous. A few minutes later, more than 50 men threw stones. Human rights group Amnesty International says the victim was a 13-year-old girl who had been raped.

Four decades ago, during the Vietnam war, Mr Duyet was in charge of the notorious Hoa Lo prison - the place where Mr McCain says he was brutally beaten and tortured during five-and-a-half years as an American prisoner of war.