Khartoum , Sudan ( CNN ) -- South Sudan 's government has gained control of a remote town that had been under attack by fighters from a rival tribe , the nation 's information minister said Monday . Some of the thousands who fled into the bush have begun to return to Pibor , said Barnaba Benjamin , South Sudan 's minister of information and broadcasting . Earlier Monday , a military official said that roughly 4,000 army and police reinforcements were on the way to Pibor after weekend attacks . The United Nations also said it sent a battalion of peacekeepers to Pibor last week amid reports that members of the Lou Nuer tribe were marching toward the town , home to the Murle tribe , after attacking the village of Lukangol . Ethnic tensions in the South Sudan state of Jonglei have flared as tribes fight over grazing lands and water rights , disagreements that have dissolved into cattle raids and abduction of women and children . Fighters first struck Pibor on Saturday , attacking a portion that was out of the reach of U.N. peacekeepers , said Col. Philip Auger of the South Sudan army . Benjamin said there were no casualties and no direct confrontation between the two tribes there , because most of the Murle had fled when they heard the Lou Nuer were approaching . The nonprofit group Medecins sans Frontieres , also known as Doctors Without Borders , was still trying Monday to reach 117 of its 130 aid workers who fled into the bush along with the populations of Pibor and Lukangol before the attack , said Sarathy Rajendran , head of the group 's South Sudan mission . Rajendran said the organization was afraid for its workers ' safety and `` very concerned '' for the people of Pibor and Lukangol . `` We believe tens of thousands are currently displaced without access to water , food and health care , '' he said . `` The situation is tense . We do n't know what is happening on the ground , so we are monitoring the situation . '' The nonprofit 's clinic in Lukangol was `` burned and looted , '' spokeswoman Emily Linendoll said , adding that its Pibor clinic `` has been targeted . '' The attack on Pibor follows reports last week that Lou Nuer fighters raided Lukangol , burning it to the ground and forcing thousands to flee toward Pibor . At least 50,000 people have fled the violence in the state that began last year , said Quade Hermann , chief of radio at Radio Miraya , a U.N.-backed radio station in South Sudan . She similarly said that the town of Pibor is secure now , though the situation there remains fluid . The people who fled remain scattered , and the United Nations is working on a plan for how to distribute humanitarian aid , Hermann said . U.N. Secretary-General Ban Ki-moon last week urged the groups to work with the government of South Sudan to find solutions . South Sudan 's vice president , Riek Machar , is leading an initiative to bridge the differences between the Lou Nuer and Murle tribes , including encouraging the armed groups to disband and go home , the United Nations has said . The violence in Jonglei state is the latest to rock South Sudan , which officially gained its statehood in July after separating from the north .
NEW : At least 50,000 people are said to have fled from the violence in Jonglei . Information minister : Some of the thousands who fled have started to return to Pibor . Earlier , an official said roughly 4,000 reinforcements were being sent to Pibor . The UN has warned that South Sudan is on a path towards civil war and called for all sides to stop fighting before it gets worse.