Two cities in Sudan are experiencing severe famine, according to a UN-backed hunger monitoring system.

The Integrated Food Security Phase Classification (IPC) declared Tuesday that the city of el-Fasher in Darfur and the town of Kadugli in south Kordofan are both facing severe famine, with more areas at risk as fighting continues to worsen across the country.

The declaration of famine in the two cities follows that of Zamzam camp in North Darfur last year by the IPC.

The United Nations secretary-general warned Tuesday that the war in Sudan is “spiraling out of control” after a paramilitary force seized the besieged and famine-stricken Darfur city of el-Fasher.

Speaking in Qatar, Antonio Guterres called for an immediate ceasefire in the two-year conflict that's become one of the world's worst humanitarian crises.

The paramilitary RSF reportedly killed more than 450 people in a hospital and carried out ethnically targeted killings of civilians and sexual assaults while seizing the city last week.

It had besieged el-Fasher for 18 months, cutting off most food and other supplies needed by tens of thousands of people.

The RSF has denied committing atrocities, but testimonies from those fleeing, online videos and satellite images offer an apocalyptic vision of their attack.

The scope of the violence remains unclear because communications are poor in the region.