The UN says it is pulling out all non-essential staff from parts of Sudan's troubled Darfur region.
An increase in violence over the last few weeks has made most of west Darfur off-limits to aid agencies.
More than two million Darfuris live in overcrowded camps, having been driven from their homes by fighting.
In south Darfur, the bodies of two more African Union (AU) soldiers have been found, taking the total number killed in a clash last weekend to four.
The AU mission is trying to monitor the many violations of a truce in Sudan's western region.
Upsurge of violence
A third of Darfur's displaced are in west Darfur, which borders Chad.
With both militia and rebels roaming its barren landscape, it has seen the worst of the recent upsurge in fighting.
In the last few weeks, displaced people have been attacked and killed by militia. Rebels have kidnapped AU soldiers and west Darfur's aid workers have been regularly targeted on its roads.
A UN spokeswoman confirmed that the deterioration in security meant that all staff not considered essential to the aid operation would be flown out.
Those who remain will be unable to leave the capital, El Geneina.