"We urge the authorities to fully investigate these reports to bring those responsible to justice and urgently act to ensure the effective protection of civilians," the UN rights office said on X.

It did not provide more details but the statement came after rights groups on Monday accused Sudan's army and allied militias of ethnically motivated assaults against civilians in the state, killing 13 people, including two children.

Sudan's army has denied the allegations.

The Emergency Lawyers, who have been documenting human rights abuses during the 20-month war between the army and rival paramilitaries, said the attacks in Um Al-Qura in eastern Al-Jazira began last week as the army advanced through the state.

On Saturday, the military recaptured the state capital, Wad Madani, pushing out the paramilitary Rapid Support Forces, who had dominated Al-Jazira since December 2023.

The lawyers' group on Monday accused the army and allied militias of detaining "a number of civilians, including women", in what they described as a part of campaigns targeting ethnic and regional communities accused of collaborating with the RSF.

They said that the abuses included "extrajudicial killing... kidnapping as well as physical and psychological humiliation and torture".

Both the army and the RSF have been accused of war crimes, including targeting civilians and indiscriminately shelling residential areas.

Though the RSF has become notorious for alleged ethnic-based violence -- leading the United States last week to accuse it of genocide -- reports have also emerged of civilians being targeted on the basis of ethnicity in army-controlled areas.

Since April 2023, Sudan has been devastated by a war that has pitted army chief Abdel Fattah al-Burhan against his former deputy Mohamed Hamdan Daglo, who commands the RSF.

The war has killed tens of thousands, uprooted more than 12 million and pushed the country to the brink of famine in what the United Nations describes as one of the world's worst humanitarian disasters.