More people have been killed in South Sudan than Darfur in recent months
By Peter Martell
BBC News, Nasir
In almost every bed in Ward Two of Nasir hospital in South Sudan, there lies a patient with a bullet wound.
"I was hit in my leg, when the soldiers started firing," said Wiyual Chol, shot like many during a recent outbreak of fighting in Upper Nile state.
"I want to walk again, but it hurts," he adds, struggling to sit up from his simple string bed.
Mr Chol is lucky - the treatment here is good, and many in the hospital took bullets in worse places than a leg.
Others lie with dressings plugging holes in their head or belly.
There have been a string of recent clashes in the south.
The United Nations say that more have died in the south in recent months from violence than in the war-torn western region of Darfur.
Some warn that the clashes are not simply localised battles, but rather a step back towards the bloody conflict out of which the region is only just emerging.
Many fear for the stability of the 2005 peace deal that ended Sudan's 22-year long north-south civil war, in which some 2 million people died.
Mr Chol was wounded during an attack on a river convoy of some 30 boats carrying UN food aid to a remote region cut off by road owing to annual rains.
The food was intended for some 19,000 displaced people of the Lou branch of the Nuer people, in desperate need of food for weeks in the town of Akobo, after fleeing separate fighting.
But barges with food had to pass Nasir, home of the Lou's long-time rivals, the Jikany branch of the Nuer.
Women and children have become targets in the clashes
Anger is high after Lou fighters massacred 71 people in the Jikany village of Torkech in May, and the sight of supplies going to their enemy caused fury.
Fuelled by rumours that arms were also hidden on boats following those with UN aid, men like Mr Chol formed a force of several hundred Jikany gunmen to ambush the flotilla soon after leaving Nasir.
The aid convoy's 150-strong military escort provided little match for the attackers, who sank at least three boats and looted more than 700 tonnes of grain.
Officials say some 60 soldiers died, but no-one knows how many others were killed.
Clashes between rival groups in the south have taken place for generations, over resources, land or livestock.
But these well-planned attacks are no simple disputes over stolen cattle.
Women and children are now also deliberately targeted - something elders say never happened in the past.
Further down the hospital ward, several young women recover from a Lou attack on their village of Torkech last month, a short distance outside Nasir.
"They attacked us at night, coming from all sides when we were sleeping," said 22-year-old Nyachiew Gatbel, cradling her young baby.
"They fired the guns everywhere, and they shot me in the leg."
The small team in the hospital, run by aid agency Medecins Sans Frontieres, are exhausted coping with the influx of casualties.
The simple brick and tin-roof hospital, a former missionary station built in the 1930s, is the only effective health care for miles around.
But the hospital is already running at double its official capacity, as it struggles to also cope with everyday cases in the grossly underdeveloped south: malnutrition, malaria, diarrhoea and pneumonia.
"We treated 33 for gunshot wounds following the attack on the boats," said Sebastian Lawrenz, the hospital's surgeon.
"In May we treated 54 after the attack at Torkech; what is tragic is that almost all were women and children, and the youngest was just two months old."
The violence comes at a critical time for Sudan, as tensions grow in the north-south unity government.
Elections are due in April 2010, the first chance to vote for many in decades.
After that, a 2011 independence referendum is due for the south, which many believe will see Africa's biggest nation split fully in two.
But distrust remains high between north and south, still divided by the religious, ethnic, ideological and cultural differences over which the civil war was fought.
Rival groups in the Upper Nile region have long argued over resources
Southern politicians claim the northern government in Khartoum wants to ferment southern divisions to scupper an independence vote.
They claim Khartoum wants to seize control of southern oil fields that lie along their shared border.
Some accuse the north of backing proxy militias it once supported in the civil war.
Southern President Salva Kiir says he is "convinced beyond any doubt" that the fighting is the work of "outside forces".
"They are designed by the enemies of peace," Mr Kiir said in early June, calling it a "diabolical strategy" to portray southerners as a people unable to govern themselves.
But rivalries such as those in Upper Nile, a region already awash with weapons, need little encouragement to spark fresh conflict.
Northerners shrug off the accusations, claiming southern politicians want to shift the blame for their failure to establish peace and restore security.
They accuse the southern government of squandering millions of dollars from its share of Sudan's oil meant to develop the war-ravaged region, and argue that the south's former rebel army has often exacerbated clashes rather than calm them.
On the wide plains dotted with cattle outside Nasir, tired looking women and hungry children gather beside a cluster of thatch huts.
Their village was burned down in fighting as soldiers retaliated against those who launched the boat attacks.
Who is really responsible for the violence, and what lies ahead for Sudan, is unclear.
However, if the past is anything to go by, it will be the most vulnerable who once again suffer most.
South Sudan is slowly recovering from years of conflict