Save the Children on Thursday warned of "a huge unseen hunger crisis" in Nigeria endangering the lives of tens of thousands of children.

Save the Children project manager Dan Stewart said that according to UN estimates 75,000 children could die and 400,000 were at risk from acute malnutrition in the coming year, as families leave behind their livelihoods to escape intensified fighting.

The warning comes ahead of an appeal by Nigeria as part of the UN's global Humanitarian Response Plan, which is due to be announced in Abuja on Friday.

Stewart, who recently returned from Nigeria, said that "children are paying the highest price" of the conflict with the militant group Boko Haram, many having to fend for themselves after having witnessed their parents being killed.

The seven-year-old insurgency has killed more than 20,000 people and created 2.6 million refugees and a humanitarian crisis that the UN estimates has 14 million people in desperate need of food aid.