A fresh wave of intercommunal fighting in South Sudan has killed and displaced "many people", a UN mission has said.
Dozens of homes in Jonglei state were destroyed, warehouses belonging to aid groups were raided, and women and cattle were abducted.
A humanitarian worker from Médecins Sans Frontières was among those killed.
A treaty aimed at ending the country's six-year civil war was signed in February, but intercommunal violence has erupted a number of times since.
The latest outbreak of violence between pastoralists, who rely on livestock, and farm workers began on Saturday in the north-eastern town of Pieri, forcing thousands of people to flee to the bush, the BBC's Emmanuel Igunza reports.
Peacekeepers were interviewing survivors in the town when fighting broke out, the UN mission said in a statement.
"The team is investigating reports that many people were killed, injured and lost their homes," it said. "However, it is difficult to verify the number of casualties given conflicting reports and claims."
David Shearer, the UN's special representative for South Sudan, said that the violence between the two groups must stop.
"While politically motivated conflict has reduced in South Sudan, intercommunal fighting has increased, causing massive suffering for families who are trying to rebuild their lives after the devastation caused by years of civil war," he said.
But outbreaks of inter-ethnic fighting have continued, threatening the fragile treaty.
Security agencies have said they've recovered hundreds of illegal firearms - including rifles, rocket-propelled grenades and hand grenades - from the warring communities.