Dozens of people have been killed in South Sudan during a shootout that broke out at a peace meeting meant to resolve disputes about stolen cattle, according to local officials.

Up to 37 people died in the northern Unity state after gunmen, reportedly including members of security forces, opened fire on the crowd involved in the United Nations-sponsored talks between local leaders, officials said on Friday.

"These guys just started shooting everywhere," said Gideon Gatpan Thoar, Unity state information minister.

Local officials from Unity and the neighbouring Lakes and Warrap states were taken by the UN for talks to the remote town of Mayendit in Unity after a spate of cattle raids, including a brutal attack last week that killed 79 people.

"The fight just started there and no one knew the cause," said Chol Tong Mayay, Lakes state governor, after gathering accounts from witnesses. "People were just shooting at each other, without knowing whose police and army they were."

The assailants, reportedly including rival bodyguards, police, army as well as armed government wildlife officers, sprayed the meeting room with bullets in the battle. The exact cause for the fight is not known.

Mayay said 22 people from Lakes state were killed and 24 wounded, but he did not know how many were killed from the two other states.

South Sudan, which declared independence from its former civil war enemy to the north in July, is reeling from multiple crises, including ethnic clashes, violent cattle raids and rebel attacks.

UN peacekeepers confirmed the fighting, but could not say how many had died. They said the gunfight erupted after one official interrupted the meeting and shouted at his counterpart.

"Four pick-up trucks carrying armed men believed to be SPLA [army] and SSPS [police] then appeared and started shooting indiscriminately at the Mayendit County Commissioner's compound," the United Nations said.

At least 15 people with gunshot wounds had been taken to a clinic in Unity state run by the Doctors Without Borders, the medical aid agency said.