A shoot-out among South Sudanese security forces using truck-mounted machineguns killed 37 people and injured a United Nations policeman on Wednesday, U.N. and government officials said on Friday.
The government in South Sudan - formed in July, six years after a peace agreement that ended decades of civil war - is struggling to assert control in a country awash with weapons and whose army is made up of former rival militias.
The shooting broke out when the commissioner for Rumbek North County interrupted a meeting about recent cattle raiding with other officials in Unity state and made "angry remarks", according to Kouider Zerrouk, a spokesman for the United Nations Mission in South Sudan (UNMISS).
"Four pick-up trucks carrying armed men believed to be (army) and (police) then appeared and started shooting indiscriminately at the...commissioner's compound," Zerrouk said in a statement.
He said it was unlikely that the U.N. team was a target, and that one UNMISS staff member attending the meeting was wounded.
A spokesman for Unity state, Gideon Gatpan Thoar, said 16 people from Unity state were killed and 21 from Lakes state.
"...the big machineguns mounted on the trucks started shooting on the people in the meeting," he said. "The Rumbek North Commissioner then went to burn down the local wildlife centre."
The Rumbek North Commissioner was not immediately available for comment.
Western donors fear South Sudan will slide into instability after the country last week shut down its oil production - the lifeline of its economy - to protest against seizures of its oil by Khartoum.
The landlocked new nation took three quarters of the oil production when it became independent but it needs to export its crude through a Sudanese pipeline and Red Sea port. Sudan and South Sudan have not yet agreed on a transit fee.