Ethiopian Prime Minister Hailemariam Desalegn (right) looks on as South Sudan's rebel leader Riek Machar (centre) and South Sudan's President Salva Kiir (left) exchange signed peace agreement documents in Addis Ababa. File picture: Goran Tomasevic

Juba - More than 60 000 people have fled their homes in war-ravaged South Sudan since the rival sides signed a ceasefire earlier this month that has failed to hold, the United Nations said on Tuesday.

Since rebel and government forces signed a truce on May 9, about 46 000 more people have been displaced inside the world's youngest nation, bringing the total since mid-December to over one million, the UN High Commissioner for Refugees said.

Another 20 000 people have fled to neighbouring countries since the truce - bringing that total to around 370 000, it said.

“The number of people fleeing fighting continues to rise,” UNHCR spokesman Adrian Edwards told reporters in Geneva, stressing that the agency saw a risk of further displacement “over the coming weeks.”

Four million people - one third of the South Sudanese population - are at risk of starvation in the young African state, the UN also said.

South Sudan only gained its independence from Sudan three years ago and has been ravaged by a conflict between rebel groups and the government since December 15.

The fighting has left many people unable to farm and cut them off from normal food sources, Edwards said.

The civil war, which started as a personal rivalry between President Salva Kiir and rebel chief Riek Machar, has seen the army and communities divide along ethnic lines, pitting members of Kiir's Dinka tribe against Machar's Nuer.

Fighting broke out hours after the two signed their second ceasefire on May 9, and hostilities have continued unabated, resulting in atrocities against thousands of civilians from both sides.

More than 131 000 South Sudanese refugees - most of them women and children - have made their way to Ethiopia, with an average of 1 000 flooding across the border each day, Edwards said.

Recent arrivals say they have fled fighting in neighbouring Jonglei and Upper Nile states, he said, adding that “those from other areas said they feared imminent attacks or food insecurity.”

The UNHCR has opened three refugee camps in Ethiopia so far this year to host them he said, pointing out that two of them are full, while a third opened just over a week ago is already hosting nearly 6 000 people.

Edwards also voiced concern for about 320 000 refugees from neighbouring Sudan who had sought a haven in South Sudan from the separate conflict in their homeland. He stressed that they were also vulnerable due to the food shortages exacerbated by the fighting in South Sudan.

Last week, international donors in Oslo pledged more than $600 million in aid for South Sudan and the countries hosting its refugees. - AFP