Two aid agencies have evacuated their international staff from a part of war-torn South Sudan fearing violence.

Doctors Without Borders and the International Committee of the Red Cross both said Saturday that they withdrew their international staff from the rebel-held town of Leer in the south of oil-rich Unity State. A statement from Doctors Without Borders said the organization is "gravely concerned about an imminent attack" on Leer, and that they have been forced to halt all their medical services at Leer hospital.

Leer is the hometown of South Sudan's rebel leader Riek Machar, whose allied forces have been fighting since December 2013 against troops loyal to the President Salva Kiir. The U.N. says that tens of thousands of people have died and 2 million are displaced by the conflict.