Myanmar's western Rakhine state has been hit by deadly violence among the country's majority Buddhists and the minority Rohingya Muslim community. The violence erupted last May following reports of rape of a Buddhist woman in which several died.
Violence resumed in recent weeks in the state, resulting in the deaths of more than 80 people and the displacement of tens of thousands of people, U.N. and official figures showed.
The aid group said medical teams in Rakhine state "are unable to provide care to many people in need due to ongoing ethnic tensions and threats against" its staff.
Additionally, thousands of patients under longer-term primary health care programs have not been getting medical services as many of those activities have been suspended since June.
"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," said operations manager Joe Belliveau.
The group said among the victims, the displaced ones remain "extremely vulnerable due to the loss of their homes and other resources."
The group said it has been providing medical services in Rakhine state for about 20 years during which more than a million people belonging to all ethnic and religious groups received treatment for malaria, tuberculosis, HIV/AIDS and maternity care.
However since the violence started, the group said it has been operating at a fraction of its capacity "largely stemming from threats and intimidation," leaving tens of thousands of residents previously receiving medical care without such care for months.