A prominent tribal leader in the disputed Sudanese territory of Abyei has been shot dead in an incident involving a rival Arab militia.
Kual Deng Majok, the chief of the Dinka ethnic group, was killed during a stand-off between the Arab Misseriya militia and UN peacekeepers.
There were also reports of UN forces being wounded.
Oil-rich Abyei abuts both Sudan and South Sudan - which seceded in 2011 - and is claimed by the two countries.
The conflict is rooted in a dispute over land between farmers of the pro-South Sudan Dinka Ngok people and cattle-herding Misseriya Arab nomads in the north.
As a result, Abyei remains under the administration of an interim UN security force.
Saturday's incident began when a convoy of South Sudanese officials looking into the future of Abyei was surrounded by the Arab militia, and the UN tried to secure their release.
A Dinka official told AFP news agency: "The top Dinka leader, Kual Deng Majok, was killed... after he was attacked by Misseriya."
A Misseriya chief also confirmed the death.
"A group of Misseriya stopped the convoy and started negotiations. Then a clash happened when a [UN] soldier shot one of the Misseriya who was readying his weapon," the unnamed chief told AFP.
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.