JUBA, South Sudan (AP) — In a blistering criticism of the United Nations mission in South Sudan, Doctors Without Borders said Wednesday that the mission is refusing to quickly move 21,000 displaced people from a U.N. base to safer grounds before the rainy season.

Doctors Without Borders said the decision by senior U.N. personnel is a “shocking display of indifference” to refugees who could be exposed to waterborne diseases and epidemics. The aid group said it questions the U.N.’s commitment to meeting the needs of South Sudan’s most vulnerable people. It also criticized the unsanitary conditions at one of the U.N. camps.