Youths armed with sticks, machetes and spears battled police in a South Sudanese town, forcing thousands of civilians to seek refuge in a UN compound, the United Nations and residents said.
A local journalist said he counted four dead bodies after the clashes broke out yesterday in the northern town of Wau, and had heard more than 15 people may have died.
South Sudan won independence from Sudan last year. Since then its government has struggled to assert control over an impoverished country the size of France that is awash with arms after decades of civil war, rebellions and tribal clashes.
Details were unclear but government spokesman Barnaba Marial Benjamin said the clashes broke out in Wau after the bodies of six Dinka tribespeople were found.
It was believed the six were among 28 farmers abducted in retaliation for another outbreak of deadly violence in the town earlier this month when security forces opened fire on a protest against plans to relocate a local authority's headquarters.
"Six bodies were brought to Wau town three days ago raising tension among various communities in Wau, which is believed to be the cause of yesterday's violence," Benjamin told a news conference in the capital Juba.
It was not immediately clear why the kidnappers had chosen to abduct those farmers.
Human rights groups regularly accuse South Sudan's army and police, a collection of former guerillas, of heavy handed tactics and human rights abuses - charges dismissed by the security forces.
Up to 300 armed Dinka youth set fire to several buildings in Wau, the main town of South Sudan's Western Bahr El Ghazal state which borders Sudan, according to the United Nations. Police used teargas to disperse the protest, while shooting could be heard, residents said.
"Some youths ... began the shooting. Police intervened and began exchanging fire with them," a witness told Reuters.
Benjamin declined to give details of any casualties, saying only the government "regretted the loss of lives and destruction of property".
Kouider Zerrouk, spokesman for the UN Mission in South Sudan, said thousands of civilians, mainly women and children, had sought refuge at the UN compound in Wau.
"They are under the protection of the mission," he said.
James Deng Dimo, a journalist in Wau, said he had counted four dead bodies and seen several injured people in hospitals.
"People are telling me that there are over 15 killed," he said, adding that he had seen people wounded by machetes, sticks and gunshot.
Hundreds of police officers patrolled the streets on Thursday after reinforcements arrived from the capital Juba by plane. Many residents were leaving the town.
"They are going to the rural areas because they fear there might be a repeat. Where I am standing I can see people carrying luggage like mattresses, beds and bags," Dimo said.
South Sudan is struggling with a severe economic crisis after shutting down its oil production, which contributed to 98 percent of state income, in January in a row with Sudan over export fees.
A lack of efficient state bodies and widespread violence has hampered plans to attract investment to a country rich in fertile land, oil and minerals.