There are two names for the life-giving river that runs through the troubled region of Abyei.
To the northern Arab Misseriya tribe it is the Bahr al-Arab but their southern neighbours the Dinka Ngok know it as the Kiir. The bitter rivalry over the land through which the river flows has made Abyei one of the most blood-soaked killing fields in Sudan's virtually uninterrupted half century of war.
Now the fighting has returned there are two conflicting accounts of a battle that threatens to unravel any hope of a peaceful divorce between north and south Sudan.
When voting ends today in the historic referendum that is almost certain to split Africa's largest country, the fate of this disputed territory will be left hanging. No one has been allowed to vote in Abyei and its future will be decided behind closed doors. In the meantime, as one diplomat put it, there are efforts afoot violently to "alter the facts on the ground".
Last Sunday, while millions of southern Sudanese queued at polling stations to make their mark for separation or unity, a full-scale battle raged in the scorched plains north of Abyei town. Alek Ngor, a mother of eight in the Dinga-Ngok village of Maker Abiyor, just north Abyei town, said the first attack came on Saturday night. "We heard the guns – everybody was scared," she said.
A police post across the stream near the village stopped the first attack. But the following morning, fighting restarted more fiercely than before.
Montoc Agok, 50, realised something was seriously wrong when he saw people fleeing across the stream: "It wasn't like Saturday; there were big guns," he said. "Rocket-propelled grenades, Kalashnikovs, big machines." He says the attackers came in three waves, some wearing "normal clothes" but others in army uniforms. He fled south to Abyei town with his family of 10.
Uniforms have become critically important in the disputed enclave which has officially been a demilitarised zone since the 2005 peace deal that ended Sudan's catastrophic north-south civil war. The treaty stipulated that neither the northern-controlled Sudanese armed forces (SAF) or the southern-run Sudan People's Liberation Army (SPLA) could enter Abyei. Only members of the joint integrated unit and conventional police were allowed. But both sides have accused the other of violating the terms of the agreement.
John, an 18-year-old policeman, was among the Abyei reinforcements sent to Maker Abiyor following reports of a skirmish last Saturday. Clearly traumatised days later by what he had seen, he said: "The fighting was heavy, I lost friends and colleagues. There were dead and wounded everywhere." He said the attackers had been wearing "green uniforms" and used "military tactics".
The Deputy Police Commissioner James Major Achuil blamed the attack on Khartoum's northern forces. "We don't have an army – we only have police," he complained. He claimed the real objective had been Abyei town and warned that his force would not be able to resist a full-scale assault.
Who and how many people died in the battle of Maker Abiyor, like everything else in Abyei, is disputed. According to SPLA officials in the South, 26 policemen were killed in two days of fighting, while as many as 50 of their Misseriya attackers died. But this is not the only account of the fighting.
Sadig Babo Nimir, a Misseriya leader speaking by telephone from Khartoum, said Sunday's attack had been a "retaliation" for an earlier unprovoked assault on Misseriya cattle-herders and a rocket attack on Arab villages. "These are not police – they are military with serious long-range weapons," he insisted.
Mr Babo Nimir, an Oxford-educated member of the Misseriya royal family, accused the SPLA of deploying 1,000 soldiers in the area. He rejected accusations that his tribesmen were being used as proxies by Khartoum.
The presence in the region of Ahmed Haroun, who like President Omar al-Bashir is wanted by the International Criminal Court for war crimes in Darfur, has also stoked fears. Now the governor of neighbouring South Kordofan, he is accused of arming and directing the Janjaweed militias that killed hundreds of thousands in Darfur.
The backwash from last weekend's fighting can be seen in Abyei town where the normally busy marketplace has been emptied of Arab traders. In some cases their places have been taken by Dinka-Ngok returnees who have come back to a town that many deserted during the 22-year civil war.
James Nyoi, 28, says the bus taking him home after years of exile in Khartoum was stopped by heavily armed Misseriya militia north of Abyei. "They took us out one by one," he said. "They beat me up and they took my money." Some of the women on the bus were taken into the bush and raped, he said.
As Sudan prepares for a north-south partition, hundreds of thousands of southerners have been moving south, often in vulnerable bus convoys. Reports have flooded in of ambushes, looting and rape. Local officials in Abyei said that 46 buses full of returnees have been held up for five days north of the enclave near the oil fields at Diffra, too scared to continue south. UN peacekeepers stationed nearby have been requested to provide an armoured escort, but local officials said they had so far refused.
Among the Dinka Ngok resentment against the UN mission in Sudan is running high. No one in Abyei has forgotten the how Zambian peacekeepers disappeared when the town was sacked by Misseriya militia assisted by northern troops, in May 2008. Burnt-out buildings still remain as a reminder of the devastation which displaced 60,000 people and took Sudan back to the brink of another ruinous war.
Oil-rich Abyei nearly wrecked the peace talks to end the civil war, with President Bashir refusing to contemplate letting it go. But the 2008 violence led to a fresh push by the international community to resolve the status of the disputed area. A year later judges at the Permanent Court of Arbitration in The Hague set Abyei's boundaries at 10,000 square kilometres, including mainly Dinka-Ngok settlements. Concessions were made to Khartoum, as the largest oil field in the region was placed in the Arab-run South Kordofan.
The decision was meant to be legally binding and the people in Abyei were told that they would vote in their own referendum on whether to join an independent South. However, Khartoum has refused to allow the vote to go ahead. While many in Abyei town are waiting for war, tens of thousands of returnees are scattered in the surrounding countryside, many without food or water.
Maria Guem, 55, who fled to Khartoum during Sudan's first civil war, has camped under a tree with her family of 15. "If it happens again we're not going to run," she said. "We have nowhere to go. We will die here where we are."
Abyei: A brief history
Once famed as the bridge between the diverse peoples of north and south Sudan, Abyei is now contested between the Arab Misseriya tribe and the southern Dinka-Ngok.
The latter are cattle herders famous for the ceremonial scars on their foreheads, who lived in relative peace with the Arab populations in Sudan's middle belt until independence.
After 1956 and the later discovery of oil, a partisan northern Arab government stoked "southern" sentiment among the Dinka-Ngok. An off-shoot of the largest ethnic bloc in the south, they provided several of the top commanders in the Dinka-led rebel army that fought the north in the civil war and many of them still wield huge influence.
The southern president, Salva Kiir Mayardit, is related to the Dinka-Ngok by marriage in a country where family ties matter.
The herders of the Misseriya are also one of the largest Arab tribes and herd nearly one-third of Sudan's vast reserves of cattle. The Misseriya have traditionally come south to cross the river they call the Bahr al-Arab during the dry season when there is not enough grass or water further north.
While this has always been accompanied by small-scale clashes, the Arab nomads now claim that these grazing lands are their own and want to claim residency in an effort to avoid having their annual dry season migration blocked.