UNITED NATIONS — The United Nations humanitarian chief said Thursday that he was alarmed that United Nations agencies had been ordered out of eastern Ukraine’s separatist-controlled Luhansk region by the “de facto authorities” there.

The statement by the United Nations official, Stephen O’Brien, said the agencies had been told to end operations and leave by Friday, and several international nongovernmental organizations had been told to leave the region by Saturday.

It is rare that United Nations agencies are ordered to cease operations in a country or region.

Russian-backed separatists occupied parts of the Donetsk and Luhansk regions in eastern Ukraine after rebels began fighting government forces in April 2014. The United Nations human rights agency said this month that at least 7,962 people had died in the conflict.