Around 1.8 million people are at risk of starvation in northeast Nigeria, mostly victims of an Islamist insurgency that is undermining efforts by the World Food Programme (WFP) to ferry in aid, it said on Friday.

The Boko Haram insurgency has killed more than 15,000 people since 2009 and forced some two million from their homes. The Nigerian army, backed by neighbours, has retaken most areas held by the group, but it has recently stepped up attacks and suicide bombings.

Aid groups entering the region in recent months have warned that shortages of food, shelter and medical care were threatening refugees with widespread famine and disease.

WFP executive director Ertharin Cousin said, in all, an estimated 4.4 million people were in need of food assistance in the northeast, though the full scale of the crisis was still unknown as some areas remained unreachable.

"The challenge is that there are areas in (Boko Haram heartland) Borno state in particular that are still inaccessible, and we have no idea of the food security situation (there),” she told Reuters.

Even in parts of the northeast held and defended by the army, Boko Haram attacks were jeopardising aid programmes, Cousin said.

Agencies