The South Sudanese government assault on the rebel-held town Nasser earlier this week drove at least 11,000 refugees across the border into Ethiopia, according to aid agencies in the western Gambella region.

Government troops and mechanized forces attacked and captured Nasser in eastern Upper Nile state on Sunday, after significant numbers of rebel fighters withdrew to outlying areas.

The town lies not far from the Ethiopian border and had served as a headquarters for rebel military commanders.

UNHCR spokesman Adrian Edwards says after the first huge influx of more than 11,000 refugees into Ethiopia in a three-day period since the attack, another wave is still waiting to cross.

"In the past 72 hours, over 11,000 people have crossed into the Ethiopian town of Burubiey, a small remote community on the shores of the Baro River which marks the border between the two countries," said Edwards.

"The refugees tell us that more people are on their way, with many amassed on the South Sudanese side of the border waiting to cross the river on one of the few small ferry boats,” he added in a press release Tuesday

“The newly arrived refugees, all ethnic Nuers, report thousands more are fleeing Nasir [some 30 kilometres from the border],” he said.

UNHCR and its partners, including the Administration for Refugee and Returnee Affairs, the Ethiopian Red Cross Society, and the UN World Food Programme, have all been rapidly scaling up their responses to meet the needs of new arrivals – some of whom are wounded and in urgent need of medical help.

Once registered, the people are being moved to Kule refugee camp further inside Ethiopia, which is reported to be approaching its maximum capacity of 40,000 refugees, while a new camp is set up for another 30,000 people.

The UN agency is hurrying to transport people due to oncoming heavy rains. The overall cost of the aid operations for South Sudanese refugees in several countries is expected to be $370 million, according to an inter-agency appeal.

Only 14 per cent of this requested amount has been received by aid agencies. The UN refugee agency says it expects to increase the appeal as the number of refugees continues to increase. 

Photo: UNHCR staff in western Ethiopia help move a wounded South Sudanese refugee, who fled across the Baro River to escape violence (UNHCR/L. Godinho)