Speaking in the Kenyan capital Nairobi, he said the conflict has resulted in death and destruction across the country and had a devastating effect on cities. Khartoum, the capital, is in “turmoil,” he added, while Darfur, where there has also been heavy fighting and looting, is “burning once more.”

“The fighting needs to stop, and to stop now before more people die and the conflict explodes into an all-out war that could affect the region for years to come,” he said.

Fighting began in Khartoum on April 15 between the forces of two generals who seized power from civilian transitional authorities in a 2021 coup: Abdel Fattah Al-Burhan, who is the head of Sudan’s regular army, and his former deputy, Mohammed Hamdan Dagalo, who commands the Rapid Support Forces, a heavily armed militia that previously shared power with the army.

The two sides agreed on Tuesday to a seven-day ceasefire, according to the Foreign Ministry of neighboring South Sudan, one of several nations, including the US and Arab states, who have been to broker an enduring truce. Previous ceasefire agreements failed to stop the fighting.

Martin Griffiths, the UN’s humanitarian chief, has traveled to Sudan to oversee relief efforts and ensure the safe delivery of aid to civilians, Guterres said.

UN staff have relocated from their headquarters in Khartoum to the city of Port Sudan on the Red Sea coast, from where they are coordinating UN and international aid efforts.

Many civilians, include Sudanese and foreign nationals, have crossed the border into neighboring states, including Egypt, Chad, Ethiopia and South Sudan. So far about 100,000 people have fled the country and 800,000 more might follow in the coming weeks, Guterres said.

According to UN humanitarian officials, 16 million people in Sudan, a third of its population, are in need of aid, and the fighting has displaced 3.7 million, mainly in the Darfur region, from their homes.

Guterres said the UN is working hard with international and regional organizations, including the African Union and eight-nation East African trade

bloc the Intergovernmental Authority on Development, to convince the warring faction to deescalate the conflict and enter into peace negotiations.

At least 512 people have been killed and 4,200 wounded since fighting began on April 15, according to the Sudanese Health Ministry. The Doctors’ Syndicate, an organization that tracks civilian casualties, said at least 295 civilians have been killed and 1,790 wounded.

Guterres said Sudan is facing a “humanitarian catastrophe” and added: “Hospitals have been destroyed, humanitarian warehouses were looted and millions are facing food insecurity.

“Aid must be allowed into Sudan and we need immediate safe and secure access in order to be able to deliver it to the people who need it the most.”