JUBA, South Sudan (AP) — More than 100 people were killed in a violence-prone region of South Sudan when one tribe attacked another while cattle were being moved across land, officials said Sunday.

Kuol Manyang Juuk, the governor of Jonglei state, said 103 people died in the Friday clash in Akobo County. Juuk said 17 of the attackers were killed and that 14 soldiers from South Sudan’s military, the SPLA, who were accompanying the cattle-moving tribe also died.

Jonglei County has been wracked by massive bouts of tribal violence for years. The United Nations says more than 2,600 violence-related deaths were reported in Jonglei from January 2011 to September 2012, and account for more than half of reported deaths in South Sudan, a country that is emerging from the shambles of a decades-long war. Jonglei state covers northeastern South Sudan.

Akobo County Commissioner Goi Joyul said the attack took place during a yearly migration in which members of the Lou Nuer ethnic group were driving cattle across the Sobat River. The commissioner said survivors of the attack saw the assailants use rocket-propelled grenades in addition to machetes and spears “thus overwhelming an SPLA force accompanying the people.”

Joyul said the attackers in Friday’s violence are believed to be members of the rebel group led by David Yau Yau. A former member of the South Sudanese army from the Murle ethnic group, Yau Yau launched a rebellion after failing to win a parliamentary seat in the Sudanese general elections in April 2010. South Sudan has repeatedly accused Sudan of backing Yau Yau and airlifting weapons and supplies to remote corners of Jonglei. Khartoum denies providing any support to the rebel group.

The International Committee of the Red Cross said it sent a surgical team to Akobo to help treat those injured in the attack.

United Nations Mission in South Sudan spokesman Kouider Zerrouk said a joint team from it and the government of South Sudan traveled to the area on Sunday and was assessing the situation.

The attacks on Lou Nuer pastoralists in Akobo came just over one year after a wave of cattle raids and counter attacks between Lou Nuer and Murle. A U.N. Mission in South Sudan report on the attacks estimates nearly 900 were killed between late December 2011 and early February 2012.

In November, the aid group Doctors Without Borders said the increasing level of violence in Jonglei was causing a humanitarian emergency. The group said health facilities are being targeted in the violence caused by inter-communal cattle rustling, fighting between government and rebels and a government disarmament process.

Michael Onyiego, Associated Press