Aid groups said Tuesday they are launching an emergency operation to help thousands of people who have crossed into Ethiopia to escape fighting in southeastern Sudan.
The International Organization for Migration said most of the estimated 20,000 refugees who have arrived in Ethiopia so far are stranded on the border with little food, water or shelter.
The U.N. refugee agency said, according to its staff, people are still entering the Assosa region of western Ethiopia from Sudan's Blue Nile state, where fighting erupted last week between government forces and rebels.
"We have received reports of tens of thousands of people having fled within Blue Nile state and northwards to Sennar state," the office of the U.N. High Commissioner for Refugees said.
"We cannot independently confirm the numbers as so far only the Sudanese Red Crescent Society has access to the displaced," it added in a statement."
The clashes broke out Thursday between armed forces and rebels linked to the northern wing of the Sudan People's Liberation Movement. The SPLM is the strongest political force in newly-independent South Sudan.
The Geneva-based International Organization for Migration said Tuesday it has sent medical and operational staff to the Ethiopian border towns of Kirmuk and Gizane. Those refugees willing to move will be relocated to an existing camp in Sherkole, 50 kilometers (30 miles) away from the border, it said.
According to the U.N. refugee agency, however, many of the new arrivals prefer to stay near the border in the hope that the fighting will end and they can return home.