Thousands of villagers have fled to camps like Yida, where humanitarian agencies have struggled to feed and shelter them.

CNN: STORY HIGHLIGHTS

On Wednesday, 616 people reached the Yida refugee camp in South Sudan - the highest number yet recorded - escaping hunger and conflict across the border in South Kordofan, a bitterly contested region of Sudan better known as the Nuba Mountains.

BBC: Fleeing from Sudan's Nuba Mountains