A humanitarian disaster is unfolding around Lake Chad, with nearly half a million children in the area facing severe acute malnutrition due to drought and a seven-year insurgency by Islamist militant group Boko Haram. The UN children's agency Unicef estimates that nearly 50,000 children in Nigeria's Borno state, Boko Haram's heartland, will die this year if they do not receive treatment.

Unicef is appealing for $308 million (£233m) to cope with the crisis. However, to date Unicef has received only 13% of what it needs to help those affected in the four countries that border Lake Chad (Nigeria, Niger, Chad and Cameroon). Over the past 18 months, these four countries have been battling to push back the Islamist militant group. At the start of 2015, Boko Haram occupied an area the size of Belgium but has since been pushed back. Most of its remaining forces are now hiding in the wilds of the vast Sambisa forest, southeast of the Borno provincial capital, Maiduguri.

As Nigerian government forces capture and secure territory, aid officials are starting to piece together the scale of the humanitarian disaster left behind in the group's wake. "Towns and villages are in ruins and communities have no access to basic services," Unicef said in a report. In Borno, nearly two thirds of hospitals and clinics have been partially or completely destroyed and three-quarters of water and sanitation facilities need to be rehabilitated.

Despite the military gains, more than two million people remain trapped in areas under the control of Boko Haram – which is trying to establish a caliphate in the southern reaches of the Sahara – or are staying in camps, fearful of going home.

Boko Haram is thought to have killed as many as 15,000 people since the launch of its insurgency in 2009. Responding to its battlefield setbacks, Boko Haram has turned to suicide bombings, many involving children. Unicef said it had recorded 38 cases of child suicide bombings so far this year, against 44 in the whole of 2015 and just four the year before that.

More from IBTimes UK