The United Nations drew up a list of 142 individuals who warrant investigation for crimes including mass rapes and sexual slavery of women and deliberate killing of scores of children.
The United Nations has accused members of South Sudan's government of committing human rights violations "amounting to war crimes" in the country's southwest.
The UN Commission on Human Rights in South Sudan urged investigations against dozens of individuals, including for abuses against children, in a report on Friday.
It said the organisation had "reasonable grounds to believe that members of the Government of South Sudan have engaged in acts ... amounting to war crimes" in the southwestern districts of Central Equatoria and Western Equatoria.
The commission has "drawn up a list of 142 individuals who warrant investigation for a range of crimes under national and international law," its chair Yasmin Sooka told the UN Human Rights Council in Geneva in a statement.
The report described grave rights abuses, ranging from mass rapes and sexual slavery of women to the deliberate killing of scores of children, including at least one infant who was beaten to death by soldiers in front of his mother.
"The notion that the localised violence is not linked to the State or to national-level conflicts, as suggested by the Government and South Sudanese military elites, is a fallacy," Sooka said.
The world's newest nation has suffered from chronic instability since independence in 2011.
The UN warned last month that it risked a return to war as interethnic violence and political infighting threaten an already fragile peace process.
At least 440 civilians were killed in brutal fighting between rival militias in the country's southwest between June and September last year, a joint report by the United Nations Mission in South Sudan (UNMISS) and the UN Human Rights Office said.
That report blamed forces loyal to President Salva Kiir and rival troops under Vice President Riek Machar, as well as "their respective affiliated militias", for the violence.
On Friday, the UN refugee agency UNHCR appealed for $1.2 billion (1.09 billion euros) to deliver humanitarian aid and protection to around 2.3 million South Sudanese living in the Democratic Republic of Congo, Ethiopia, Kenya, Sudan and Uganda.