"We are deeply disturbed by what we witnessed and heard throughout our visit.
A team of UN rights experts said Friday they were "deeply disturbed" by atrocities committed by all warring parties in South Sudan and called for perpetrators to be brought to justice.
During a 12-day visit to the country, which this month entered its fifth year of a devastating conflict, the team encountered harrowing tales of torture, revenge killings, abduction of women and children and sexual violence.
"We are deeply disturbed by what we witnessed and heard throughout our visit. The deprivation and range of sexual violence are hard to describe, people are targeted and suffering just for being who they are," one of the rights commissioners, Andrew Clapham, said in a statement.
The statement came a day after main warring parties meeting in Addis Ababa agreed to implement a ceasefire from December 24, during negotiations billed as a "last chance" to stop the conflict.
The rights commission welcomed the call to lay down arms but "remains gravely concerned over the lack of accountability for serious crimes which is fuelling impunity throughout the country," said team chair Yasmin Sooka.
"Those responsible for this war against civilians must be stopped with the perpetrators of these horrific acts brought to justice."
In the northwestern city of Wau, an 89-year-old widow told the team how her husband and two sons were shot in front of her, while a 60-year old woman recounted being gang raped by several soldiers and left for dead.
The commission also heard of young men being gang-raped or forced to rape relatives in front of family members.
"Those perpetrating these crimes seem to be intent on breaking all social norms resulting in societies being torn apart," said Sooka.
The team of rights experts is due to release a full report on its findings in March next year.
South Sudan's leaders fought for decades for independence, but once they achieved it in 2011, a power struggle between President Salva Kiir and his former deputy Riek Machar led to all out civil war in 2013.
A peace deal was signed two years later but collapsed in July 2016 when fresh fighting in the capital Juba forced then first vice president Machar into exile.
The renewed conflict saw violence spread across the country, and armed groups multiplying.
Tens of thousands have been killed and some four million displaced since the war began.