The head of the UN mission in Sudan, Volker Perthes, said on Tuesday that the violence in the vast Darfur region of western Sudan could constitute "crimes against humanity".
Fighting has been raging in Sudan since mid-April between the army commanded by General Abdel Fattah Al-Burhane and the paramilitary Rapid Support Forces (RSF) of General Mohamed Hamdane Daglo.
They are mainly concentrated in the capital Khartoum and in Darfur, a region where local militias, tribal fighters and armed civilians have joined the clashes.
The conflict has claimed more than 1,800 lives in the country, according to the NGO ACLED, and displaced two million people, according to the UN.
"As the situation in Darfur continues to deteriorate, I am particularly concerned about the situation in El-Geneina (West Darfur) where the violence has taken on ethnic dimensions", said the UN envoy in a statement.
"The large-scale attacks on civilians based on their ethnic origins, allegedly committed by Arab militias and armed men in RSF uniforms, are very worrying and, if proven, could constitute crimes against humanity," he warned.
Last week, the Sudanese government declared Mr. Perthes persona non grata, accusing him of being biased in the conflict. But Stéphane Dujarric, spokesman for the UN Secretary General, said his status remained "unchanged".
While several truces have not been applied, NGOs are reporting a deterioration in the humanitarian situation in Khartoum and Darfur.
"What is happening in El-Geneina and Kutum (further east) must give rise to an international investigation", Darfur governor Minni Minnawi, a former rebel leader now close to the army, said on Twitter on Saturday.
In the early 2000s, General Daglo, head of the Janjaweed militia, conducted a scorched earth policy in Darfur on the orders of the then dictator Omar al-Bashir.
The war left around 300,000 people dead and nearly 2.5 million displaced, according to the UN. In 2013, the Janjaweed officially gave birth to the RSF, the army's paramilitary auxiliaries.
Generals Al-Burhane and Daglo joined forces in the 2021 putsch to oust the civilians with whom they had shared power since the fall of Bashir in 2019. But differences then arose and, in the absence of an agreement on integrating the RSF into the army, degenerated into war.