The United Nations said on Monday it was investigating reports that 25 people had been killed in South Sudan's central Gok state in clashes between two tribal factions.
Thousands of people have already died in South Sudan from a four-year civil war pitting forces loyal to incumbent President Salva Kiir and his former deputy, Riek Machar.
A quarter of the country's population of 12 million has also been uprooted and displaced by the violence that has largely unfolded along ethnic lines.
A UN official in South Sudan's capital Juba, spoke on condition he should not be named, told Reuters they had received reports on Saturday that 25 civilians had been killed and 27 wounded in clashes between Waat and Ayiel, two ethnic groups that are part of South Sudan's Dinka Gok tribe.
He did not say what triggered the clashes, but said they occurred in the state's Cueibet county and that they had also received reports South Sudan's military had been deployed in the area to try to restore order.