Sudan's army and the paramilitary Rapid Support Forces (RSF) have both attacked civilians, used torture and made arbitrary arrests, according to the 19-page report that said it was based on 182 interviews with survivors, their relatives and witnesses.

"The gravity of these findings underscores the urgent and immediate action to protect civilians," the chair of the U.N. factfinding mission, Mohamed Chande Othman, said. He called for an independent and impartial force to be deployed without delay.

Both sides have dismissed past accusations from the U.S. and rights groups, and have accused each other of carrying out abuses. Neither immediately responded to a request for comment on Friday, or released a statement in response to the report.

The mission called for the expansion of an existing U.N. arms embargo which currently just applies to the western region of Darfur. The war that started in Khartoum in April last year has spread to 14 out of 18 of the country's states.

The reported abuses may amount to war crimes or crimes against humanity, the mission said.

The mission also said it had also found reasonable grounds to believe that the RSF and its allied militias had committed additional war crimes including sexual slavery and the recruitment of child soldiers in the conflict.

The fact-finding team said it had tried to contact Sudanese authorities on multiple occasions but had got no answer.

The conflict began when competition between the army and the RSF, who had previously shared power after staging a coup, flared into open warfare.

Civilians in Sudan are facing worsening famine, mass displacement and disease after 17 months of war, aid agencies say.

U.S.-led mediators said last month that they had secured guarantees from both parties at talks in Switzerland to improve access for humanitarian aid, but that the Sudanese army's absence from the discussions had hindered progress.

The report is the three-member mission's first since its creation in October 2023 by the United Nations Human Rights Council in Geneva.

A group of Western countries including the United States and Britain will call for its renewal at a meeting beginning next week, with diplomats expecting opposition from Sudan which considers the war an internal affair.