At least 10 people have been killed in fighting between rival ethnic groups in Sudan's disputed oil-producing region of Abyei, officials say
The clashes between Arab nomads and the southern Dinka Ngok people are the first since a deal between the two sides was agreed last month.
Abyei lies on the border between north and south Sudan.
The region did not take part in last month's referendum in which southerners voted to split from the north.
Abyei is due to vote on whether to join the north or south at a later, unspecified date.
The Dinka Ngok think it belongs in the south, while the nomadic Arab Misseriya see it as northern.
The heart of their dispute is about grazing rights for cattle, which are central to both communities' traditions and economies.
Both sides accused each other of starting the recent clashes.
Deng Arop Kuol, the chief administrator for Abyei from the Dinka Ngok community, told Reuters news agency a Misseriya group had attacked a settlement in the early hours of Sunday morning.
But senior Misseriya official Saddig Babo Nimr told the agency the southern army had started the fighting by attacking a nomadic camp.
Officials have warned the death toll could rise.
"There is still fighting going on. The situation is very bad, and we cannot stop to count the dead," Mr Kuol told AFP news agency.
UN troops in Abyei have been boosted over the last few months because of the tensions.
North and south Sudan have suffered decades of conflicts driven by religious and ethnic divides, with an estimated 1.5 million people killed in the civil war.
The referendum on southern secession was agreed as part of the 2005 deal to end the 21-year civil war.