Sudanese militias are carrying out daily raids on refugee camps in Chad, says the United Nations refugee agency.
The war in Sudan has created a huge refugee problem
The UNHCR says its relocating the refugees deeper into Chad to avoid the attacks.
About 600,000 people have fled their homes in Darfur western Sudan following a year-long fight between rebels and government forces.
Some 10,000 refugees have already been moved away from the volatile border as part of an ambitious plan.
On Sunday, Arab militia killed one person and stole herds of cattle after attacking two sites.
According to the refugees, the raid was conducted by a group of 35 armed men who also stole 100 herd of cattle, the refugee agency said.
The agency has identified three new sites where the refugees will be moved within the next 10 days.
Some 100,000 Sudanese refugees have been sheltered in camps in Chad.
Rebels of the Sudan Liberation Army (SLA) and the Justice and Equality Movement (Jem) accuse the Arab-dominated government of ignoring the black African inhabitants of Darfur.