The U.N. refugee agency says violence over the past two weeks in eastern Chad has driven as many as 20,000 people from their homes.
In a statement Friday, the agency blamed the displacement on cross-border attacks by Janjaweed militia in the Borota region, and on what it called inter-communal hostilities.
The U.N. reported similar violence in eastern Chad late last year.
The U.N. agency's Chad representative, Serge Male, says the situation poses a direct threat to camps in the region that house thousands of Sudanese refugees from neighboring Darfur.
He says his agency's resources are insufficient to meet what he calls "overwhelming" humanitarian needs.
The U.N. says there are now 100,000 Chadians displaced within their own country.
Along with the Janjaweed attacks, eastern Chad has also been the site of many clashes between Chad's army and rebels opposed to President Idriss Deby.
U.N. High Commissioner for Refugees Antonio Guterres has called for an international initiative to improve security in eastern Chad.