Could Abyei dispute reignite Sudan war?
Recent clashes in Sudan's disputed border region of Abyei highlight the biggest danger to the south's drive to independence following years of north-south conflict.
Abyei is home to the Dinka Ngok, a subsection of the south's largest ethnic group, the Dinka.
The Misseriya, who are northern nomads, travel through the region as they take their cattle to greener pastures in the south.
Most years there are clashes when the Misseriya take their cattle through lands the Dinka Ngok consider belong to them.
Kuol Deng Kuol, the paramount chief of the Dinka Ngok, says further fighting in Abyei could suck in the northern and southern armies.
"Our southerners will not let us down, and the northerners will not let the Misseriya down, so in this case it's a north-south war," he states in a matter-of-fact way.
It seems clear southerners have voted for separation in their referendum - but no-one can work out what to do with Abyei.
The region, which is on the border between north and south, ought to have had its own referendum on which half of the country to join.
If a solution is not found, it is possible a new north-south civil war could break out.
The Abyei referendum has not happened yet, essentially because President Omar al-Bashir's National Congress Party and the former southern rebels, the SPLM, couldn't agree whether the Misseriya could vote or not.
A number of alternative solutions have been proposed by the US and the AU mediation led by former South African President Thabo Mbeki.
None have been accepted so far - and with no clear idea when Abyei's future would be decided, violence broke out.
On 7-9 January, there was a succession of deadly clashes between the Misseriya and police units from the southern armed forces, helped by young men from the Dinka Ngok.
The fighting, in the village of Makir Abior, about 10km (6.2 miles) to the north of Abyei town, killed more than 30 people.
"As far as the UN is concerned, Abyei is one of the key flashpoints," says Squadron Leader Adam Thomson of the UN military.
"The fighting we have seen has been very localised, though quite intense."
A recent UN patrol tried to find out more - a convoy including two armoured personnel carriers chugged along dirt roads, spraying up dust onto the bright orange acacia trees.
But at a bridge two kilometres short of the village, they were turned back by southern police and armed civilians.
Their reception in the Misseriya village Goli was no better: Men in civilian clothes with AK 47s slung over their backs shouted at the peacekeepers to leave.
Tensions are clearly high, despite a deal signed by the Dinka Ngok and the Misseriya in Kadugli last Thursday.
That set out the conditions for the Misseriya's migrations to the south to begin again, but did not address the bigger question of Abyei's future.
There is a history of conflict here.
Roman Catholic priest Fr Peter Suleiman looks at the jagged edges of the hole the mortar round punched in the warehouse in the grounds of his church in 2008.
Civilians blamed the UN for not protecting them, and that mistrust still lingers today.
The 2008 fighting in Abyei was probably the biggest breach of the 2005 north-south peace agreement to date.
Fr Peter's church was severely hit, dozens of people died, and Sudan almost slipped back into the all-out war the country has experienced for most of its independent history.
Many analysts have similar fears about the latest clashes here.
More and more civilians from both sides are arming themselves, and talking of fighting for their rights.
Local leaders are determined, to say the least.
"Abyei us for is a matter of survival, so we will fight until the last man," says Sadig Babo Nimr, one of the Misseriya leaders.
"Abyei for us, you either live on the surface or you are buried underground, and we're ready to sacrifice everything."
He does say that negotiations are the preferred first option, and the problems can be sorted out at a local level if Khartoum and Juba do not get involved.
Dispute over resources
Several Dinka Ngok notables told the BBC their people were preparing to defend themselves, and would never give up their land.
There is some evidence Mr Bashir's National Congress Party and the SPLM are trying to avoid the worst.
Another interpretation is that they are not prepared to let a squabble in a small region derail a bigger peace process.
But many Dinka Ngok think the NCP is pushing the Misseriya to fight them, and the Misseriya leaders say the same of the southern army.
The main issue in Abyei used to be oil.
But a ruling by the Permanent Court of Arbitration in the Hague redrew the boundaries of Abyei, placing many of the oilfields outside the region.
Instead the dispute is about identity and resources.
Elsewhere in Sudan religion has provoked conflict, in particular because the largely non-Muslim southerners rejected what they saw as the imposition of Sharia law.
But in Abyei this is less of a factor.
The Misseriya are Muslim, but so are some Dinka Ngok - though the majority follow Christianity or traditional religions.
The split here is not predominantly on religious lines - instead it is ethnic and local. Muslim Dinka Ngok seem just as keen to join the south as the others.
As with many places in Africa, the battle for scarce resources between nomadic cattle-herders and settled communities can be bitter.
This has been exacerbated by the stark choices presented by Sudan's upcoming division.
Meanwhile, life is getting harder.
"The road to the North is closed and things are getting difficult in the market, life is becoming expensive," Fr Peter says as he finishes his tour of his still-damaged church.
"We hope these things will be solved, because it is the innocent people who suffer."
Both Sudan and the South are reliant on their oil revenues, which account for 98% of South Sudan's budget. But the two countries cannot agree how to divide the oil wealth of the former united state. Some 75% of the oil lies in the South but all the pipelines run north. It is feared that disputes over oil could lead the two neighbours to return to war.
Although they were united for many years, the two Sudans were always very different. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.
Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.
The health inequalities in Sudan are illustrated by infant mortality rates. In South Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.
The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.
Throughout the two Sudans, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.
Conflict and poverty are the main causes of food insecurity in both countries. In Sudan, many of the residents of war-affected Darfur and the border states of Blue Nile and South Kordofan, depend on food aid. The UN said about 2.8m people in South Sudan would require food aid in 2013. The northern states tend to be wealthier, more urbanised and less reliant on agriculture.