War and hunger threaten to "consume" Sudan, where hundreds of thousands of malnourished children are at risk of dying, as fighting between rival generals rages on, the United Nations has warned.

The conflict between the army under General Abdel Fattah al Burhan and the paramilitary Rapid Support Forces (RSF) commanded by Mohamed Hamdan Dagalo broke out on April 15.

"The war in Sudan is fuelling a humanitarian emergency of epic proportions," Martin Griffiths, under-secretary-general for humanitarian affairs and emergency relief coordinator, said on Friday.

"This viral conflict –- and the hunger, disease and displacement left in its wake –- now threatens to consume the entire country."

Conservative estimates from the Armed Conflict Location & Event Data project say nearly 5,000 people have been killed.

But the battles have prevented the recovery of the bodies of many others thought to have died.

In the four months since fighting broke out, more than 4.6 million people have been forced to flee their homes, according to UN figures.

"The longer the fighting continues, the more devastating its impact. Some places have already run out of food ," Griffiths' statement said.

"Hundreds of thousands of children are severely malnourished and at imminent risk of death if left untreated."

The UN official said that in Kadugli, in South Kordofan state, "food stocks have been fully depleted, as clashes and road blockages prevent aid workers from reaching the hungry."