Paul Kuon's escape from his war-torn nation was the most brutal of journeys, with the South Sudanese rebel fighter forced to dodge gunfire as he trekked with his wife and two young children.

But after his two month-long ordeal, passing scores of dead bodies and spending days without food or water to reach the relative safety of an Ethiopian refugee camp, Kuon is readying to return to fight.

"There is no choice... we will not give up, we will continue fighting," said Kuon, a member of one rebel force that is fighting against the government.

"What was done by the government in Juba is not correct, they tried to kill each individual, brothers and sisters were killed," he told AFP, standing among hundreds of refugees under a cloud of buzzing flies, in a rapidly growing camp just across the border in western Ethiopia's Gambella region.

Kuon is leaving his family behind in the camp to return to a bloody civil war in the world's youngest nation, in which thousands have already been killed.

Despite the brutal suffering the war has caused -- displacing nearly one million people, many without sufficient food or medical care -- troops have refused to lay down their arms, violating a ceasefire deal signed in January.

Slow moving peace talks between the government and rebels failed to resume as scheduled on Thursday in the comfort of a high-end hotel in the Ethiopian capital, although mediators insisted they would restart soon.

So far they have made little, if any, progress.

READ: South Sudan peace talks begin amid Kiir fears on power

"You cannot leave this fight because I've left my brothers there fighting, they are fighting for our freedom," said Chuot Mach, a bony-chested rebel soldier from a separate rebel force, flashing a toothless smile.

"I will go and fight until we get a solution."

South Sudan's government has been at war with rebel groups since December 15, when a clash between troops loyal to President Salva Kiir and those backing sacked vice-president Riek Machar descended into full-scale fighting.

The conflict has taken on an ethnic dimension, with the Dinka people -- Kiir's tribe and the country's biggest -- largely allying with the government against Nuer forces loosely tied to Machar.

Aid agencies warn of a growing humanitarian crisis, with observers saying the country faces possible famine if warring parties do not heed the ceasefire.

Refugees desperate for food and medicine have poured into neighbouring countries, including Ethiopia, where over 72,000 have arrived since mid-December.

READ: Where shall we sleep tonight? The refugee burden

A new camp opened in late February is already full, and officials are seeking to expand existing settlements or open new ones on the dusty and heat-cracked earth.

Ethiopia could receive up to 300,000 refugees in total, UN refugee agency chief in the country, Moses Okello said.

The UN estimates that $350 million (251 million euros) will be needed to respond to the South Sudan refugee crisis by the end of the year.

READ: UN body needs $59m for South Sudanese refugees

But what is alarming is that "the condition in which (the refugees) are arriving is getting progressively worse," Okello told AFP.

"Our fear is that the group that will come after this will be really in a bad, bad way," he added.

Recruitment of child soldiers is a major concern, said Okello, noting there are few young men in the camps.

"Our fear is that there could be people that are staying behind to fight, possibly including children," he said.

Both sides have been accused of atrocities and war crimes, and this month the African Union launched an inquiry into human rights abuses.

South Sudan was born less than three years ago, splitting from the rump of Sudan after more than five decades of on-off civil war.

But the desire to fight on remains for many, with many using the same rhetoric once used in the 1983-2005 civil war.

Nyatuach Chol left her three adult sons in the key oil-producing state of Upper Nile region to fight in the war, while she walked with her daughter and grandchildren for a month, surviving on leaves and little water until they reached the camp.

"I support my children, because they are fighting for freedom," she said, sitting under the shade of a UN tent in a tattered green floral dress.

She has not heard from them since she left three months ago, and does not know if they are alive or dead. But she accepts their fate.

"I cannot worry, the one who dies, dies, while the one who survives will come and get me," said Chol, emaciated and grey-haired.

"This is a cause for all of our people, not only my sons."