kutapalong bangladesh head u.n. refugee agency say saturday shock terrible violence inflict rohingya refugees flee myanmar say suffer would last far long time take satisfy basic need 420,000 rohingya muslims flee bangladesh since aug. 25 attack rohingya militants rakhine state trigger myanmar crackdown unite nations brand ethnic cleanse visit sprawl kutapalong refugee camp southeastern bangladesh close myanmar border unite nations high commissioner refugees filippo grandi say rohingyas tell stories really strike fear people carry go see back myanmar tell reuters camp refugees live thousands tarpaulins cover hill rice paddies parent kill families divide wound inflict rap perpetrate women lot terrible violence occur take long time people heal wound long satisfy basic need grandi say speed scale exodus myanmar leave hundreds thousands live dire condition poor part poor country u.n aid agencies scramble give people shelter get feed prevent outbreak disease senior u.n. official say friday estimate 200 million would need help refugees bangladesh six months aid workers fear humanitarian crisis also unfold rakhine state though myanmar restrict access rohingyas trace root back generations myanmar stateless minority mostly strip citizenship predominantly buddhist country tensions communities simmer decades explode violence several time recent years myanmar leader aung san suu kyi face barrage international criticism plight speak forcefully violence rein security force little power myanmar dismiss accusations ethnic cleanse say tackle insurgents accuse start fire attack civilians well security force grandi july call myanmar grant rohingyas citizenship also ask rohingya refugee bangladesh would take return refugee say myanmar need restore citizenship fundamental right violence continue right group amnesty international say friday new satellite image videos show plume smoke still rise villages rakhine state unhcr chief meet rohingya refugees bangladesh camp