The United Nations is deploying peacekeeping troops to the remote town of Pibor in South Sudan, saying it faces an imminent attack by thousands of fighters engaged in ethnic clashes in the war-torn region.

Ethnic tensions in the South Sudan state of Jonglei have been inflamed by tribes fighting over grazing lands and water rights - disagreements that have dissolved into a number of cattle raids during which women and children were abducted.

About 6,000 members of the Lou Nuer tribe are marching on Pibor, home to the Murle tribe, said Lise Grande, the U.N. deputy humanitarian coordinator for South Sudan. An advance group of about 500 fighters have taken up positions outside the town, she said Friday.

"We deemed that there was a very serious risk to civilians (and) in support of the government of South Sudan's primary responsibility to protect civilians, we have gone ahead and deployed a battalion-size force in Pibor with the aim of deterring violence and helping the government to protect its own people," she said.

The deployment of peacekeeping troops follows reports earlier this week that Lou Nuer fighters raided the own of Lukangol, burning it to the ground and forcing thousands to flee toward Pibor.

"We are so alarmed by the situation that during the course of the afternoon we have reinforced our positions in Pibor," Grande said.