STEFAN HEUNIS via Getty Images A boy suffering from severe acute malnutrition at one of UNICEF's nutrition clinics in the Muna informal settlement on the outskirts of Maiduguri on June 30.

The people of northeast Nigeria are about as tough as they come. Their remote region is ground zero for many of the world’s most vexing problems, including an Islamic militant insurgency, crippling poverty, and the devastation wrought by climate change.

Now, the United Nations warns that the area may face a new calamity: famine.

People in the region “are used to coping with extreme hardship, exploiting every and any option they can to keep their families going,” U.N. Humanitarian Coordinator Stephen O’Brien told the U.N. Security Council on Wednesday. “But … this suffering has pushed them to the absolute limit ― it is unlike anything they have felt before.” He called it “a humanitarian catastrophe.”

The hunger crisis has been growing since militant group Boko Haram captured swaths of northeast Nigeria in 2014, crippling agriculture and the local economy and displacing more than 2 million people. The insurgency by Boko Haram extremists, who in recent years have killed more people in terror attacks than the Islamic State, has left more than 20,000 people dead.

The fighting has further isolated the region from the rest of the world. That means the humanitarian crisis brewed mostly out of sight until Nigeria and its allies began pushing Boko Haram out of camps, villages and towns over the last year.

Aid groups are just beginning to reach areas that were recaptured, and representatives said they’ve been horrified by what they’re finding.

In mid-June, more than 1,000 people were evacuated from the Nigerian town of Bama so they could receive medical treatment. Aid group Doctors Without Borders said 39 percent of the town’s children were severely malnourished.

“When we saw that, we realized the severity, and it was a shock,” said Isabelle Defourny, Doctors Without Borders director of operations. A week later, the aid group’s staff reached the town for the first time with a military escort and found more than 1,200 graves, including 480 for children, had been dug in the past year.

Humanitarian officials with decades of disaster experience said the situation was among the worst they’d ever seen.

“What we have uncovered and assessed is deeply, distressingly alarming, even for those of us who have witnessed such depths of humanitarian need before,” O’Brien told the U.N. Security Council. “I have been traveling throughout this region on and off for the past 37 years [and] I have never heard such fear and desperation. This is a new terrible.”

Bruno Jochum, Doctors Without Borders general director, called it “a large-scale humanitarian disaster” and urged the U.N. to set up an emergency food pipeline. “Probably the medical and epidemiological indicators are the worst we are facing today in the world,” he said.

STEFAN HEUNIS via Getty Images A young girl at the Muna settlement for displaced people. UNICEF estimates that some 50,000 children in northeast Nigeria are at risk of dying from malnutrition and related causes without immediate assistance.

“This is about as bad as it gets,” Toby Lanzer, U.N. assistant secretary general in the Sahel, told The Guardian this month. “There’s only one step worse ― and I’ve not come across that situation in 20 years of doing this work ― and that’s a famine.”

The numbers are daunting. The U.N.’s Children Fund estimates that nearly a quarter-million children in the region are severely malnourished, and some 50,000 will die without immediate treatment.

That warning, stark as it may seem, may not capture the full extent of the crisis. Only half of the estimated 500,000 to 800,000 people in displacement camps in northeastern Nigeria’s Borno state are reachable by aid agencies, Defourny said. Most of them are living in isolated towns destroyed by fighting, taking shelter in the remaining structures while under military guard. In the town of Bama, for example, 15,000 people, mostly women and children, are living in a hospital compound with no latrines, poor access to water, and little food, Defourny said.

Outside the camps, aid groups have no clear picture of how many people are still trapped in their villages, or how bad their situation is. Thousands continue arriving in urban areas, many in poor health recounting stories of ongoing fighting and starvation back home.

How did the situation get so bad?

First, the Boko Haram insurgency destroyed the local economy. Farmers couldn’t farm, markets shut down, and millions fled to escape the fighting.

Second, neither Nigerian authorities nor international aid agencies have yet mobilized a humanitarian response robust enough to meet the need. This is partly due to ongoing fighting. The U.N. on Thursday temporarily suspended aid operations in Borno state, with the exception of Maiduguri, after Boko Haram militants attacked a humanitarian convoy, injuring a UNICEF employee and a contractor.

But some aid workers criticize humanitarian organizations, including U.N. agencies, for being too slow to recognize the extent of the crisis and to respond. Additionally, the Nigerian government didn’t make clear its need for aid, claiming that Boko Haram had been defeated and the displaced population could return home.

Some ex-government officials say Nigerian authorities deliberately covered up the extent of the crisis to avoid international embarrassment.

“We were not aware of the gravity of the situation. We were not fast enough,” Defourny said. “People in this region have already lost a lot of life due to political violence, and today they are dying because of something else, malnutrition, that is avoidable.”

STEFAN HEUNIS via Getty Images A woman carried her daughter to the nutrition clinic in Muna. Over 2 million people have been displaced by the deadly insurgency by militant group Boko Haram.

Nigerian officials in recent weeks have sounded the alarm with more urgency. Last month, Nigeria’s minister of health declared a nutrition emergency in Borno state, and the local government has appealed for international assistance.

Aid groups have urged the government to lift bureaucratic barriers in order to facilitate the entry of aid, as reports begin to circulate that corruption ― soldiers demanding protection money, or government workers pilfering aid supplies ― is slowing the response.

“Taking from these people is like stealing from a corpse,” said one police officer in a Nigerian displacement camp, according to Foreign Affairs.

STEFAN HEUNIS via Getty Images A makeshift hut in the Muna settlement. Aid workers say groups have not moved fast enough to bring aid to the region, and the government underplayed the crisis.

With limited aid, people in northeast Nigeria are doing all they can to help their community survive. About 90 percent of displaced people in the region are staying with extended families or community members, and schools and empty buildings in Maiduguri have been repurposed to house displaced families.

Samantha Power, the U.S. ambassador to the U.N., on Wednesday recalled a university security guard she met in northeast Nigeria, who had taken in more than 50 relatives displaced by the violence.

“He is a national hero and there are tens of thousands of such heroes across the region,” Power told the U.N. Security Council. “I think we of greater means should all be inspired by these heroes to do much, much more.”