Doctors Without Borders Calls UN Humanitarian Response in CAR "Unacceptable"

Says tens of thousands of people are without the help they need

(CNN) -- Medecins Sans Frontieres slammed the United Nations Thursday for what it said was an "unacceptable" humanitarian response to the crisis in the Central African Republic.

In an open letter, the group, also known as Doctors Without Borders, said it had "deep concern" over the United Nations' humanitarian agencies' "appalling performance" in the country over the past year.

This failure, it said, has left tens of thousands of vulnerable people without the help they need.