The United Nations' human rights envoy to the country, Tomas Ojea Quintana, said a wave of attacks against aid organisations had choked off health, water and food supplies, increasing the vulnerability of the Rohingyas.
"Recent developments in Rakhine State are the latest in a long history of discrimination and persecution against the Rohingya community which could amount to crimes against humanity," he said in a statement yesterday.
The exodus has deepened an already dire health situation for hundreds of thousands reliant on international medical relief, with some 140,000 in the camps, as well as more than 700,000 vulnerable people in isolated villages severely affected.
Quintana said water supplies could reach critical levels within a week in some camps for displaced people, the vast majority of whom are Muslim, and urged the authorities to do more to ensure the safety of humanitarian personnel.
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Tensions have been heightened by Myanmar's first census in three decades, which has stoked anger among Buddhists that it might lead to official recognition for the Rohingya, a Muslim minority viewed by the authorities as illegal immigrants from Bangladesh.
Quintana said the government's decision not to allow Rohingyas to register their ethnicity in the census meant that the population tally was not in accordance with international standards.
The outspoken envoy, who is approaching the end of his six-year tenure, urged the government to address "systematic discrimination and marginalisation" of the Rohingya in his final report on the country.
Rohingya Muslims in Rakhine are subject to a web of restrictions on everything from movement and employment to marriage and in some areas family size.