The United Nations humanitarian chief says he is "alarmed" that U.N. agencies have been ordered out of the Luhansk region in eastern Ukraine by the "de facto authorities" there.

Stephen O'Brien's statement Thursday says the U.N. agencies have been told to end operations and leave by Friday.

O'Brien also says several international non-governmental organizations have been told to leave Luhansk by Saturday. His statement does not name them.

O'Brien adds that U.N. operations in the region of Donetsk are also in peril. He says "a decision by the de facto authorities in Donetsk on the U.N.'s future operations remains on hold, and all U.N. agency operations have been suspended."

O'Brien calls the failure of authorities in the separatist-dominated regions to allow humanitarian access "a blatant violation of international humanitarian law."