There are wars that seem to slip under the wire almost unnoticed – where human rights abuses are rife and you would expect them to command far greater global attention.

Last week’s UN report into South Sudan is a case in point. An almost endless litany of human rights abuses, its 200-plus pages make for the most dismal reading, a portrait of the world’s youngest state as one of the latest additions to the category of failed state.

Despite the most recent attempts at a ceasefire and political accommodation with the multiplying warring parties fighting for control of the new nation’s resources – not least its oil reserves – the report, for the UN Commission on Human Rights in South Sudan, depicts routine and continuing abuses that may amount to serious war crimes.

The stark figures on conflict insecurity are bad enough: 60% of the population experience food insecurity, while a population of just over 12 million people includes 2.2 million refugees and 1.9 million internally displaced.

One of the world’s worst humanitarian crises, South Sudan will need $1.5bn (£1.1bn) in aid for citizens still inside the country and $2.7bn for its refugees, says the UN. In some areas, 65% of women and 36% of men may have been sexually abused, according to the report.

South Sudan has also become the most lethal place for humanitarian workers, with 14 killed in the country last year.

But it is in the granular detail that the horror of South Sudan, eight years after independence, emerges. Stories of the most gross violations of human rights appear on almost every page, associated with conflict in places like the Equatorias and Unity State, which have long been a focus of violence.

“There is a confirmed pattern of how combatants attack villages, plunder homes, take women as sexual slaves and then set homes alight – often with people in them,” said commission chair Yasmin Sooka in a statement about the report’s findings.

A newly released child soldier stands with his rifle during a release ceremony in Yambio. Photograph: Stefanie Glinski/AFP/Getty Images

“Rapes, gang rapes, sexual mutilation, abductions and sexual slavery, as well as killings, have become commonplace in South Sudan.”

Dark even as that summary sounds, it does not come close to depicting a reality where – as the report suggests – a quarter of victims of sexual violence, used by all sides to sow terror, are children as young as seven. Children are also increasingly being recruited by the warring parties as soldiers.

The report tells of people being held for years and tortured in secret, vermin-ridden detention centres; of people hacked to death, children run down by tanks, babies being drowned, starved or smashed against trees.

During a visit to South Sudan last year, I interviewed victims of human rights abuses, including those fleeing from recent fighting in Unity province who had taken shelter in the vast expanse of marshes around Nyal.

The tales those survivors told were horrific, but the details collected by the UN commission’s members, and the sheer scale of the human rights violations listed, eclipse by far those stories.

“There is no doubt that these crimes are persistent because impunity is so entrenched in South Sudan that every kind of norm is broken, even raping and killing the young and the elderly,” said commission member Andrew Clapham at a news conference in Geneva on Wednesday.

The commission added that the army, national security, military intelligence, rebel forces and affiliated armed groups had committed serious human rights breaches, and said it had drawn up a confidential list of suspects that included army and opposition commanders, two state governors and a county commissioner.

Although South Sudan’s main warring parties signed a peace deal in September, widespread violence, especially rape, has continued.

Describing rapes committed during the fighting in Unity state last spring, the report said: “One witness recalled that: ‘They even raped one woman who had just delivered a baby. I understand that her baby was one to two months old. They even raped girls aged between seven to 10 years old. The soldiers rammed a piece of wood into the vagina of one woman after they had raped her. They hung dead bodies from trees – both men and women.’

“Some women died as a result of being raped, while one witness recounted how a newly wed young woman was shot and killed because she refused to be gang-raped.”

Women and children displaced by fighting camp outside while they wait to be registered for food aid at an emergency distribution site in Thanyang, Unity state. Photograph: Kate Holt

It is not only in the fighting in the countryside that appalling abuses have taken place. The commission described accounts of prisoners being killed by security forces in and around the capital Juba’s notorious Blue House security headquarters.

One witness described killings at a site near Yei where detainees were being held in containers.

“When they want to kill you, they take you out of the container. There is one excavator who will dig a big hole. The militaries will take the first five in the line and instruct them to line in front of the hole.

“A group of militaries with guns will line in front of them and start shooting, some other militaries will use panga – it’s a machete – and hit, cut people. So, they all fall into the hole. Some fell alive before being hit by panga. Then the militaries gave order to the excavator to close the hole. Some people were buried alive. I saw that several times.”

If there is one faint glimmer of hope in all this, it is that the report represents the first step in a process that may culminate with war crimes prosecutions. The commission announced it would continue to build on its findings.

“This evidence may be used beyond South Sudanese bodies – it may be available on request to regional and state parties for future prosecutions,” said Commissioner Barney Afako. “With sustained political will and effective leadership, the transitional justice framework and mechanisms can help to bring accountability, reconciliation and healing as South Sudanese deal with the past and secure their future stability and prosperity.”