GENEVA - Flagrant rights violations by Sudan's warring parties require the deployment of an "independent and impartial force" to protect millions of civilians driven from their homes, UN experts said.
An independent fact-finding mission uncovered "harrowing" violations by both sides since April last year "which may amount to war crimes and crimes against humanity", they said.
The conflict pits the national army led by General Abdel Fattah al-Burhan against the paramilitary Rapid Support Forces of his former deputy, Mohamed Hamdan Daglo.
It has triggered one of the world's worst humanitarian crises.
Tens of thousands of people have been killed, and the experts said eight million civilians have been displaced while a further two million people have fled to neighbouring countries.
Mohamed Chande Othman, chair of the fact-finding mission, created late last year, called for "urgent and immediate action to protect civilians".
"Given the failure of the warring parties to spare civilians, it is imperative that an independent and impartial force with a mandate to safeguard civilians be deployed without delay," Othman said.
The mission found evidence of "indiscriminate" airstrikes and shelling against civilian targets including schools and hospitals as well as water and electricity supplies.
"The warring parties also targeted civilians... through rape and other forms of sexual violence, arbitrary arrest and detention, as well as torture and ill-treatment," the mission said.
"These violations may amount to war crimes."
In August, the United States convened talks in Geneva aimed at ending the brutal war, achieving progress on aid access but not a ceasefire.
It also announced visa sanctions on an unspecified number of individuals in South Sudan, including government officials, accused of obstructing the delivery of humanitarian aid for 25 million Sudanese facing severe hunger.
The UN-mandated experts based their findings on testimony from dozens of survivors of the fighting now in Chad, Kenya and Uganda -- but not in Sudan, where authorities failed to respond to four requests to visit.
Sudan's government also declined to comment officially on the mission's findings.
Its report "should serve as a wake-up call to the international community to take decisive action to support survivors, their families and affected communities, and hold perpetrators accountable," Mona Rishmawi, a member of the mission, said in a statement.