Doctors Without Borders says it has been expelled from Burma and the decision leaves tens of thousands of lives at risk.
The move is linked to the humanitarian group's work with the long-persecuted Rohingya Muslim population in the state of Rakhine.
The group said in a statement late today it is "deeply shocked" by the decision.
Doctors Without Borders says HIV and tuberculosis clinics in Rakhine, Shan and Kachin states, as well as the main city of Rangoon, were closed today, denying patients life-saving medicines.
The group is Burma's main provider of HIV drugs, treating 30,000 people, and it described the impact as devastating.
Burma criticised the group over its handling of patients following an attack in the remote northern part of the state last month.