The United Nations says about 20,000 people have crossed into Uganda to escape fighting in the eastern Democratic Republic of Congo.
A statement from the U.N. refugee agency Sunday says the refugees are camped at two locations and lack food, water, shelter and sanitation.
The fighting erupted Thursday when forces loyal to renegade DRC Army General Laurent Nkunda occupied several towns and villages.
DRC government soldiers chased them out of some areas but clashes have continued, with U.N. peacekeepers aiding the government.
The fighting is around the town of Rutshuru in North Kivu province.
U.N. and government troops have been trying to subdue various rebel and militia groups in the area in preparation for nationwide elections later this year.
Some information for this report was provided by AP and Reuters.