Some 50,000 Sudanese have fled into southeastern Chad in the past week following fresh tribal conflict in the restive Darfur region, UN and Chadian officials said on Friday.
Melissa Fleming, a spokeswoman for the UN High Commission for Refugees, said the fighting had spread as each side received reinforcements from tribal allies and had become more violent, with entire villages being razed.
A total of 74,000 refugees had fled to Chad in the past two months, she said.
"People are arriving wounded and telling us their houses are destroyed and their villages completely burned down, with many people killed," she told a news conference in Geneva.
The refugees have fled to an arid area along the Chad, Sudan and Central African Republic border.
"The area they are arriving in is very remote. They left with nothing: there is no water, no food. They are sleeping under trees," Fleming said, adding there was a risk of disease.
General Moussa Haroun Tirgo, the governor of the Sila region of southeastern Chad where the refugees have fled, told Reuters that about 52 wounded had arrived since Thursday.
"The situation is worrying given that the zone does not have enough medical infrastructure," Tirgo said. "We're evaluating the needs with the help of NGOs but the situation is very serious."
Conflict has ravaged Sudan's western Darfur region since 2003 when mainly non-Arab rebels took up arms against the Arab-led government, accusing it of politically and economically marginalizing the region.
Violence has subsided from its peak in 2003 and 2004, but a surge has forced more than 130,000 people to flee their homes this year, according to the United Nations.