At least 41 people were killed and dozens wounded when rebels raided three cattle camps in South Sudan's Jonglei state, authorities said.
The attackers, armed with automatic weapons and suspected to be loyalists of militia leader David Yau Yau, shot indiscriminately at the camps and stole thousands of cattles, Xinhua reported citing officials as saying Sunday.
The critically wounded people were rushed to hospital by the United Nations mission in the country.
Yau Yau, the leader of Murle tribe, rose in rebellion against South Sudan's government after he failed to win a parliamentary seat in the general election in 2010.
According to the UN, more than 1,500 people have been killed in Jonglei since South Sudan gained independence in 2011.