Several people were wounded in South Sudan when gunmen attacked civilians sheltering inside a UN peacekeeping base in the war-ravaged town of Bor, the UN said.
The top UN aid official in South Sudan, Toby Lanzer, said he was outraged by what he said was an "attack of armed youth in Bor on civilians seeking protection".
He added: "We will not be deterred."
Almost 5,000 civilians are sheltering inside the fortified base of the UN mission in South Sudan (Unmiss) in the town, one of the most bitterly contested regions in the four-month long conflict in the world's newest nation.
Mayor Nhial Majok said at least 14 people were wounded, but added that the number could be higher.
"Local youth were demonstrating ... there was shooting of guns," Majok told AFP, adding that at least 14 young men had been seen with gunshot wounds. He said the demonstrators had clashed with peacekeepers inside the base, but it was not immediately clear who had fired the shots.
"Some of the youth were armed," Majok said, adding that the situation was now returning to calm.
The conflict in South Sudan has left thousands dead and forced around a million people to flee their homes since fighting broke out on 15 December in the capital Juba, before spreading to other states in the oil-rich nation.
More than 67,000 civilians are still seeking UN protection from ethnic attacks. The fighting is between soldiers loyal to president Salva Kiir and mutinous troops who sided with Riek Machar, who was sacked as vice-president in 2013.
The conflict has also taken on an ethnic dimension, pitting Kiir's Dinka tribe against militia forces from Machar's Nuer people. Bor town, capital of Jonglei state, has swapped hands several times during the conflict.
The UN secretary general, Ban Ki-moon, has warned that more than one million people are at risk of famine in the troubled country.
