Civilians recounted gang rapes on an industrial scale, toddlers being swung against tree trunks until they were dead and families barricaded in their homes to be burned alive.
When a mother fled from one inferno carrying a small baby she was shot and the child crushed to death by a soldier, an eye-witness said.
The testimony was gathered from 100 people who survived an offensive in Unity State, in the northern Greater Upper Nile region of the country, between April and July this year.
Government troops have been accused of giving free rein to youth militias, unleashing a wave of systematic slaughter. The epicentre of the violence was Mayendit and Leer counties, areas held by the opposition.
Witnesses described civilians being slaughtered in their villages. Some were burned alive in their tukuls – traditional mud huts which often have a thatched roof. A man believed to be over 90 had his throat slit.
Nyaweke, a 20-year-old woman, said she saw soldiers shoot dead her father and kill a number of children in Thonyoor, in Leer
“There were seven men (soldiers) who collected the children and put them into a tukul (a round mud hut) and they set the tukul on fire. I could hear the screaming. They were four boys. One boy tried to come out and the soldiers closed the door on him. There were also five boys whom they hit against the tree, swinging them. They were two [or] three years old. They don’t want especially boys to live because they know they will grow up to become soldiers.”
In a separate incident in Rukway village, also in Leer, a couple and their two grandsons were burned alive in a house.
Their daughter attempted to flee with her baby but she was shot and her child stamped to death.
Even those who fled their villages had little chance of survival. Soldiers used amphibious vehicles to hunt those who had fled into swamps.
The violence took part in Unity State, in the north of the country
Nyalony, an elderly woman, told Amnesty she witnessed soldiers killing her husband and two other men: “When the attack started, early in the morning while we were sleeping, my husband and I ran to the swamp together.
“Later in the morning, after the fighting was over, the soldiers came into the swamp looking for people, and sprayed the area where we were hiding with bullets.
“My husband was hit; he cried out in pain. He was still alive, though, and the soldiers caught him, and then they shot him again and killed him. He was unarmed and wasn’t a fighter; just a farmer.”
Women and young girls said that they were abducted before being gang raped, sometimes for many weeks. Others were used as slaves to cook and clean for their captors.
A 60-year-old man found his niece after she had been sexually assaulted by five men. She was just 13.
“My brother’s daughter was raped and she was going to die,” he said.
“When they raped her, we came and found her and she was crying and bleeding … she couldn’t hide … she told me she was raped by five men. We could not carry her and she could not walk.”
There were also reports of sexual mutilation and castration.
Nyatap, who is around 32, gave a graphic account of her ordeal. Eight months pregnant, she was abducted with her five-year-old son and daughter, seven.
“There were 20 soldiers,” she said. “The other women who are not pregnant were raped. There was another lady… she was three months’ pregnant and she miscarried. She was raped by 10 men. I saw it happen. They were just raping her under another tree.
“They put us in one compound…. there were other ladies… They would take turns raping them.”
Soldiers accused of carrying out the slaughter are also said to have looted and burned on a vast scale, making it virtually impossible for survivors who had fled to return to their homes.
Amnesty claims that the situation was enabled by South Sudan’s government failing to prosecute suspected war criminals for previous massacres in 2016.
Four people had been identified but no action had been taken.
Joan Nyanyuki, Amnesty International’s Regional Director for East Africa, said: “A key factor in this brutal offensive was the failure to bring to justice those responsible for previous waves of violence targeting civilians in the region.
“Leer and Mayendit counties have been hard hit in the past, and yet the South Sudanese government continues to give suspected perpetrators free rein to commit fresh atrocities. The result has been catastrophic for civilians.”
Amnesty has called for immediate end to all human rights abuses.
Joanne Mariner, Amnesty International’s Senior Crisis Response Adviser, said: “It’s impossible to ignore the cruel reality – if the South Sudanese authorities had acted on our warnings back in 2016, this latest wave of violence against civilians in Leer and Mayendit might have been avoided.
“The only way to break this vicious cycle of violence is to end the impunity enjoyed by South Sudanese fighters on all sides. The government must ensure that civilians are protected and that those responsible for such heinous crimes are held to account.”she said.