PIBOR, South Sudan, Jan. 2 (UPI) -- Villagers in South Sudan have been warned by the United Nations to flee fighters from a rival ethnic group bent on carrying out a vendetta over cattle raiding.
The BBC reported fighters from the Lou Nuer ethnic group were pursuing members of the Murle group.
Tens of thousands of Murle have fled Pibor after the town was attacked by Lou Nuer Saturday.
The British broadcaster said an estimated 1,000 people have been killed in recent months in revenge attacks over cattle raids.
Lise Grande, U.N. deputy humanitarian coordinator in South Sudan, said about 6,000 Lou Nuer fighters "far outnumbered" several hundred U.N. peacekeepers and government troops.
She said several flanks of attackers had moved in a southeasterly direction from Pibor "almost certainly looking for cattle" and burning huts, and while the main part of Pibor had been held, a Doctor Without Borders clinic had been "overtaken."
Grande said the United Nations was keeping tabs on the movement of Lou Nuer and warning people in the path of the fighters to "disperse into the bush for their safety."
The BBC said many of the Lou Nuer fighters were believed to be chasing the Murle who had fled Pibor.
Some of those who were displaced -- mainly women, children and the elderly -- had been killed, the BBC said, though the number of deaths could not be verified.
The Lou Nuer were still occupying parts of Pibor, a resident said.
South Sudan President Salva Kiir has called on the Lou Nuer to stop their advance, while the government said it was deploying more troops and an additional 2,000 police to Pibor.
