About 200,000 people have been displaced in ethnic clashes since mid-December in the northeastern Ituri province of the Democratic Republic of Congo, a humanitarian source says, as escapees spoke of burnt villages and victims being hacked to death.
Hema herders and Lendu farmers have been locked in violence in Ituri for decades, with tens of thousands killed from 1999 to 2003.
In 1999 a fight over land rights in the gold-rich province drew in militias and led to 60,000 deaths and about 600,000 people displaced, according to Human Rights Watch. The conflict led to the deployment of a European Union peacekeeping force in 2003.
Another humanitarian source said "on an average 800 people are arriving daily" in Bunia, the main city in the region, due to the fighting.
"Since mid-December about 200,000 people have been displaced in Ituri due to the violence," the first humanitarian source said.
The UN in Kampala meanwhile said over 22,000 refugees had fled to Uganda recently to escape violence has left several dead and villages torched.
At least four refugees drowned while crossing the waters of Lake Albert between the two nations, the UN refugee agency, UNHCR, said, expressing concern.
"Last week, over 22,000 Congolese crossed Lake Albert to Uganda in three days, bringing the total number of people from the DRC arriving in the country to about 34,000 since the beginning of the year," UNHCR said Tuesday.
"The refugees use small canoes or overcrowded and rickety fishing boats, often carrying more than 250 people and taking up to 10 hours to cross."
A UNHCR spokesman in Geneva expressed serious concern saying thousands were lined up along the banks of the lake to flee. Babar Baloch said the refugees were flocking to the Ugandan village of Sebagoro, about 270 kilometres north-west of the capital Kampala.
"Refugees crossing to Uganda talk of growing attacks against civilian populations, as well as killings and destruction of private property," a UN statement read.
"UNHCR staff also received many reports of civilians being hacked to death and killed with arrows."
Ituri is part of DRC's deeply troubled eastern region that includes the restive North and South Kivu provinces, where militias hold sway over huge areas.
There are about four million displaced people in the sprawling central African country which has been racked by rebellion, civil war and despotic rule since its independence from Belgium in 1960.
The latest violence comes amid uncertainty over the future of President Joseph Kabila, who has ruled since 2001.
On Tuesday, the head of the country's national election commission said the long-delayed polls due in December would not be held if there were no electronic voting machines.