Human rights watchdog Amnesty International has demanded the immediate release of a Bangladeshi cartoonist whom the military-backed interim government arrested for allegedly insulting Islam. Mohammed Arifur Rahman, a former cartoonist for the Bengali-language daily Prothom Alo, is "a prisoner of conscience" who was detained for exercising his legitimate right to freedom of expression, Amnesty International said in a statement Friday. Security officials arrested Rahman on Sept. 18 after hard-line Islamic groups protested against one of his cartoons that they said mocked the Prophet Muhammad.