Myanmar's military is shelling villages and preventing civilians from getting food and humanitarian help, amid an intensifying crackdown on the rebel Arakan Army in the restive northwestern state of Rakhine that has pushed thousands from their homes, Amnesty International has said. The human rights group said on Monday its investigations also found that the security forces had used vague and repressive laws to detain civilians in its battle against the Arakan Army, an ethnic Rakhine group that is fighting for more autonomy.