"We estimate about 10 people are dying every day ... Most of those who are dying are children," Modibo Traore, the head of the UN's Office for the Coordination of Humanitarian Affairs, said of the Gety camp in Ituri district.
More than 40,000 civilians have taken refuge at the camp from marauding militias who rape and kill.
"There is a big problem of lack of food. Most of the displaced haven't had any food for a week and we don't know when the next distribution will be," Traore told Reuters.
Some aid workers fear the death toll may rise sharply.
The grim comments came only two weeks after the biggest UN peacekeeping force in the world helped supervise landmark elections.
The July 30 elections, the country's first free polls in 40 years, were the culmination of a peace process that followed a devastating 1998-2003 war which killed 4 million people in one of the world's worst humanitarian disasters.
Despite the logistical and security challenges, millions of Congolese voted in relative calm. But the final results could take several weeks and violence and hunger are ever-present.
"The last food distribution was done by WFP [the World Food Programme] on the 14th July but by the end of the month, it had run out," Thierry Dumont, field coordinator for Medecins Sans Frontieres-Switzerland, said from Bunia, Ituri's main town.
"Unfortunately, we don't know, and they don't know when they will be able to do a proper distribution. It won't be before the end of August," he said.
Gety's displaced have been forced to return to their fields to gather what food they can, running the gauntlet of hostile militia fighters despite recent efforts to establish a truce.
A fortnight ago a family of five living near Gety was shot dead and their bodies burned in their hut.
The people sheltering in Gety, around 40 kilometres south of Bunia, are among 1.7 million Congolese who have been displaced by years of war and violence.
In a reminder that the elections have not ended the suffering or bloodshed of many Congolese, thousands were forced to flee fighting over the weekend between the army and troops loyal to a renegade general, Laurent Nkunda.
That fighting, not far from the city of Goma nearly 400 kilometres south of Bunia, was between soldiers from the army's 9th brigade and those from a brigade loyal to Nkunda, who are all meant to be integrating together into a new national army.
The new army, supposed to restore order in Congo, is plagued by political, ethnic and factional rifts and corruption, its soldiers often poorly paid and equipped.
The 17,000 UN peacekeepers are spread thinly across the mineral-rich former Belgian colony.
Joint operations with the Congolese army against militias have been accused of adding to civilian suffering and the number of displaced people.