Nigerian security forces were warned hours before the raid that led to the kidnapping of more than 240 school girls that an attack was about to be launched, Amnesty International has said. The human rights group accused the Nigerian authorities of ?gross dereliction of duty? as it claimed the security forces knew of the raid almost four hours before it took place but did too little to stop it. The ?damning? claim was made as Amnesty released details of information it had been given during...