Lying on a small bed next to her mother, 14-month-old Aisha Usman stares blankly, her eyes sunk in their sockets and rib cage visible.

She is the latest arrival at a treatment centre for severely malnourished children in Nigeria's Northeast, where a long running Islamist insurgency has uprooted millions, forcing farmers to abandon fields and causing food shortages.

Some 1.74 million children under the age of 5 face acute malnutrition in the area, the United Nations Office for the Coordination of Humanitarian Affairs says.

The militant Boko Haram group and its offshoot Islamic State West Africa Province have been fighting Nigerian security forces in the northeast for over a decade, displacing more than 2 million people and killing hundreds of others, aid agencies say.

At the treatment centre at Damaturu Hospital, in the Yobe state capital, Aisha's mother Fatima said there were days when her family goes to sleep hungry because of a lack of food.

That is because in her Babangida village, some 50 km from Damaturu, Islamist insurgents forced villagers to abandon their farms, she told Reuters. She used to fetch firewood for sale but says that stopped as it became too dangerous to venture into the forest.

"Sometimes we are getting food to eat, and at times we don't," the 35-year-old said.

Her daughter weighs 4.7 kg (10 lb), less than half the average weight of children her age. Some of the little girl's organs were shutting down when she arrived at the hospital, a doctor said.

She has been given an injection and started receiving food via a tube, and the doctor said she was slowly responding and improving.

The United Nations' OCHA needs $1 billion this year to assist 5.5 million people, including women and children, with food aid in the three states of Borno, Adamawa and Yobe.

The OCHA has raised only 42% of the required funds eight months into the year, according to a briefing to reporters.

Some international donors have shifted funding elsewhere, including Ukraine, Ethiopia and Afghanistan, which are also facing increased humanitarian needs, the OCHA says.

Up to 5,000 children in Nigeria's Northeast, however, are at risk of dying in the next two months if funding does not come through, said John Mukisa, a nutrition sector coordinator for U.N. agencies.

Across from Fatima's bed, 21-year-old Sahura Hassan brought her son to the Damaturu treatment centre because he had stopped eating, had a fever, could not sit and was severely dehydrated.

"Most of the problem we notice in these local government areas is due to poor access to food due to the insecurity, and there is food insufficiency in each of the households," Japhet Udokwu, the doctor in charge of the treatment centre, told Reuters.

Farming sustains livelihoods in the Northeast, but insecurity, the rising cost of fertiliser and diesel, as well as flooding and drought due to changing climate, have combined into a powerful force that is upending lives.

Federal government says it is winning the fight against insurgents in the Northeast and that some areas have now been cleared of militants and are safe for villagers to return and farm.

Reuters