KILO 18 REFUGEE TRANSIT CAMP, South Sudan Refugees say Sudan's armed forces are attacking villages in the Blue Nile border state with warplanes, helicopters and troops, killing civilians and torching settlements, in a counter-insurgency campaign that rights activists say could include war crimes.
Sudanese army and civilian officials, who strongly deny the allegations, in turn accuse the rebels of using civilians as human shields and as pawns to win international sympathy.
In over a dozen interviews, refugees who have arrived in South Sudan over the last three weeks told Reuters that Sudan's armed forces had burned their homes in the Ingessana mountains region, scattering people into caves and forests.
They are victims of a conflict that erupted last year, around the time Sudan and South Sudan split apart under a 2005 peace deal, and which shattered six years of relative peace and cast the 1,800 kilometer (1,125 mile) frontier into turmoil.
The fighting between government forces and rebels, whom Khartoum accuses the South of backing, has complicated already-fraught talks between the two countries to resolve a raft of issues related to partition.
It has also alarmed aid agencies who fear a humanitarian disaster in Blue Nile and in South Kordofan, another border state, as food stocks dwindle.
Saura Mayas is one of the 35,000 new arrivals in South Sudan's Upper Nile state who have been on the march for months. Cradling one of her malnourished twin babies, Mayas said she has been running since December, when Sudanese troops attacked her village, Jam.
"In the afternoon, after lunch, the plane came and bombed the village, then the soldiers started to burn all the houses and the people ran into the forest," she said, a leather talisman hanging from her neck.
"In the evening when I buried myself in the trees, the big guns shot into the forest," she said through an Ingessana translator.
Events in the border regions are difficult to verify first-hand because the areas are remote and Sudan restricts access for independent observers.
But the refugees' accounts echoed some of those that advocacy group Human Rights Watch published in April that it said "indicates potential war crimes may have occurred".
Sudanese officials dismiss those charges, saying their forces are in the border states to help civilians, not hurt them. They point out that many people have actually fled north from the conflict, suggesting they feel secure there.
Rabie Abdelati, an official at Sudan's Information Ministry, denied the armed forces were burning villages but said the rebels might be.
"They are not following the law. They are not respecting civilians. They make a lot of destruction," he said of the insurgents. "I cannot imagine the armed forces would burn villages."
ARC OF UNREST
While Khartoum and Juba bicker, often violently, over oil, cash, citizenship, and lines on a map, Sudan's army has been battling guerrilla armies in an arc of unrest stretching from the Ethiopian border in the east to the Chadian border in the west.
During the 1983-2005 civil war, the insurgents in Blue Nile and South Kordofan fought as the 10th and 9th divisions of the southern rebel Sudan People's Liberation Army.
But when Sudan and South Sudan split up in July, 2011, Khartoum took the two states, home to a mix of Muslims, Christians and others who follow traditional African beliefs.
Fighting in South Kordofan erupted in June last year, and the rebels rebranded themselves the Sudan People's Liberation Army North (SPLA-N). The Blue Nile insurgents returned to the bush in September, reigniting a dormant conflict over resources, political rights, ethnicity, religion, and culture.
The rebels, who aim to topple Sudan's President Omar Hassan al-Bashir, say they are fighting a Khartoum elite who have left their regions undeveloped and marginalized. Khartoum accuses them of trying to sow chaos at Juba's behest.
Despite official denials, independent research group Small Arms Survey has gathered information which it says suggests the countries have both supported insurgents.
In April, it outlined evidence indicating Juba had continued to give military and logistical support to the SPLA-N after partition, noting rebel commanders were often seen in the South Sudanese capital.
The conflict has been a major hurdle to talks between the two countries to settle issues including the location of the border, the status of citizens in one another's territory and how much the landlocked South should pay to export oil via Sudan.
"It's all about power in the end," one aid worker said, sketching on a hand-drawn map the movement of the front line as the counter-insurgency campaign sweeps through the state, pushing refugees out of the mountains and into the South.
RAINY SEASON COMING
Sitting in the speckled shade of a thorny tree in a crisp white robe, 32-year-old Idriss Hamoda said he left his village of Magaja when the "Jallaba" - a derogatory term for Sudanese Arabs - attacked in early January, killing 12 people and burning the village to the ground.
First Antonov cargo planes bombed the village, and then helicopter gunships shot people, Hamoda said. The soldiers came after.
"Those who were not able to run, they slaughtered them like hens," Hamoda said as women passed by wearing wraps of vibrant, saturated colors.
Several of the other refugees interviewed also recounted helicopter and warplane attacks on their villages.
Abdallah Hassan, 28, from Amar Atom, said his grandmother was burned alive in her house. "By the time we came back, we only found the bones," he said.
Wrong-footed aid agencies are scrambling resources to help this month's surge in refugees from Blue Nile, who now number about 100,000. Medical charity Medicins Sans Frontieres (MSF) describes the situation as a full-blown humanitarian crisis.
"We see people dying every day. We see people dying of malnutrition, we see people dying of dehydration, and we see a vast majority of the population being quite ill, mostly with diarrhea," MSF's emergency coordinator Tara Newell said.
The coming rainy season will be a mixed blessing, turning roads to gluey mud but providing a lifeline to thirsty refugees.
Like many others, Mayas and her remaining family were forced to eat tree leaves and roots and drink from puddles. One of her children died of dehydration. Another, Amere, born on the side of the road, died of diarrhea at midnight on Monday.
Clutching her remaining child in a white MSF tent, Mayas implored Bashir to put an end the fighting. "I am not a soldier. Why did he do that? Tell him to stop the war."
(Additional writing and reporting by Alexander Dziadosz; Editing by Will Waterman)