The aid group, Doctors Without Borders says its medical staff have been threatened and stopped from reaching violence-hit areas in Myanmar, leaving tens of thousands without essential health care.
France's Doctors Without Borders (Medecins Sans Frontieres) said on Monday it faces "ongoing antagonism generated by deep ethnic divisions."
More than 100,000 people have been displaced and many killed since Myanmar’s ethnic violence erupted in June after Buddhist extremists attacked the Muslim Rohingya minority community.
“That we are prevented from acting and threatened for wanting to deliver medical aid to those in need is shocking and leaves tens of thousands without the medical care they urgently need," MSF operations manager Joe Belliveau said.
Belliveau said threats in letters, pamphlets and on the social networking site Facebook used "highly vitriolic" language which caused staff to fear for their safety.
Last month, second round of violence erupted against minority Muslims in the western Rakhine state, where dozens of houses were torched.
Some ethnic Rakhine leaders have campaigned against international aid agencies in recent months, claiming they favor the Rohingya. Aid groups deny the accusations.
The government in Myanmar refuses to recognize Rohingya Muslims as citizens and holds the opinion that the only solution to the crisis is to send the one-million-strong community to other countries willing to take them.
Rohingyas are said to be Muslim descendants of Persian, Turkish, Bengali, and Pathan origin, who migrated to Myanmar as early as the 8th century.