At least 37 people have been killed in South Sudan during a shoot-out at a peace meeting aimed at ending recent violence, officials said.
Officials from three states and the UN had met for talks in the remote town of Mayendit in Unity state in an effort to reduce inter-ethnic tensions.
Those killed in the gun battle included civilians, but most were police.
The talks were called after a series of clashes, including one in which 74 people died earlier this week.
Thousands of people have been displaced in the violence.
According to the UN, Friday's incident occurred after a row broke out at the meeting. Four trucks arrived filled with gunmen, who opened fire indiscriminately.
The gunmen included policemen from different units, soldiers and security guards, according to AFP news agency.
One member of the UN peacekeeping mission was wounded in the shoot-out.
South Sudan's Deputy Defence Minister, Majak D'Agoot, told the BBC it was triggered after "a problem occurred" between police from Unity and police from neighbouring Warab state.
"Each side thought they were attacked," he said. "It was a problem largely produced by lack of effective command and control."
Correspondents say security in South Sudan, which became independent from Sudan last July, is one of the country's greatest challenges.
The BBC's James Copnall in South Sudan's capital Juba says a lack of discipline is perhaps unsurprising as fighters make the transition from a rebel movement to a government force.
Hundreds of people have also been killed in a series of tit-for-tat cattle raids in Jonglei state in recent weeks.
Officials from three states and the UN had met for talks in the remote town of Mayendit in Unity state in an effort to reduce inter-ethnic tensions.
Those killed in the gun battle included civilians, but most were police.
The talks were called after a series of clashes, including one in which 74 people died earlier this week.
Thousands of people have been displaced in the violence.
According to the UN, Friday's incident occurred after a row broke out at the meeting. Four trucks arrived filled with gunmen, who opened fire indiscriminately.
The gunmen included policemen from different units, soldiers and security guards, according to AFP news agency.
One member of the UN peacekeeping mission was wounded in the shoot-out.
South Sudan's Deputy Defence Minister, Majak D'Agoot, told the BBC it was triggered after "a problem occurred" between police from Unity and police from neighbouring Warab state.
"Each side thought they were attacked," he said. "It was a problem largely produced by lack of effective command and control."
Correspondents say security in South Sudan, which became independent from Sudan last July, is one of the country's greatest challenges.
The BBC's James Copnall in South Sudan's capital Juba says a lack of discipline is perhaps unsurprising as fighters make the transition from a rebel movement to a government force.
Hundreds of people have also been killed in a series of tit-for-tat cattle raids in Jonglei state in recent weeks.