The United Nations special envoy on human rights in Burma says the treatment of the country's Rohingya Muslims could amount to crimes against humanity.
The statement follows attacks on international aid workers in western Rakhine state, where tens of thousands of Rohingya live in squalid displacement camps.
Buddhist mobs last month forced hundreds of aid workers to flee. The government has prevented many from returning, cutting off critical supplies for the camps.
In a statement, U.N. envoy Tomas Ojea Quintana said that within a week water shortages could reach critical levels. He urged Burma, also known as Myanmar, to do more to protect the workers.
Quintana said the developments are just the latest in a "long history of discrimination and persecution against the Rohingya community, which could amount to crimes against humanity."
The U.N. views the Rohingya as one of the world's most persecuted minorities. The government denies the group many basic rights, including citizenship. It views them as immigrants from Bangladesh.
Buddhist-Muslim violence erupted in Rakhine state in 2012 and has since spread to other parts of the country. The fighting has killed at least 240 people and displaced 140,000 others, mainly Rohingya.
Last month's mobs broke out following rumors that an international aid worker desecrated a Buddhist flag. Many majority Buddhists were already upset at the aid agencies, claiming they gave preferential treatment to Rohingya.