Gunmen have killed at least 51 people – mostly women and children – in the latest clashes in South Sudan’s troubled Jonglei state, regional Governor, Kuol Manyang has said.
At least 22 others were injured after attackers raided and burned the village of Duk Padiet, he added.
The wounded have been evacuated to Juba, the capital, he said.
A series of retaliatory attacks between ethnic groups in the region has displaced tens of thousands of people.
“We are expecting more to be injured because they ran to the villages last night,” Mr Manyang said.
Officials told AFP news agency the killings were carried out by the Murle group on ethnic Dinkas, as revenge for a deadly raid last month on the town of Pibor.
It is understood that some Dinkas accompanied some 6,000 Lou Nuer warriors who attacked Pibor.
The cycle of violence has lasted months and killed hundreds of people. It began as cattle raids but has spiralled out of control.
BBC East Africa correspondent Will Ross says the attacks are getting increasingly violent and neither the government nor the United Nations peacekeepers seem capable of stopping them.
Officials point out that Jonglei is the size of Bangladesh and that it is impossible to protect every village.
Some of the reinforcements sent to the region have been deployed in Murle areas around Pibor but the revenge attacks are now happening in Dinka and Lou Nuer communities.
South Sudan, which gained independence last year, has declared Jonglei a national “disaster area”, while the UN has launched an emergency operation to help those affected by the fighting.