Boko Haram is engaged in “almost unimaginable” violence and brutality that has forced massive numbers of people to flee their homes and led to unprecedented numbers of people in need, the U.N. humanitarian chief said Wednesday.

Stephen O'Brien said the U.N. estimates that over nine million people across the Lake Chad Basin spanning parts of Nigeria, Niger, Chad and Cameroon need humanitarian assistance, including about 2.8 million who fled violent attacks in their towns and villages.

Boko Haram’s “most heinous, barbaric and unconscionable” violence and brutality has also resulted in serious human rights violations and economic disruption in a fragile region already impacted by the world’s highest population growth and worst poverty, climate change and the massive drying up of Lake Chad which straddles the four countries, he said.

O'Brien told the Security Council that Nigeria is bearing “the brunt of the crisis” despite significant government efforts, with Nigerians accounting for seven million of the nine million people needing humanitarian help.

The 1.7 million children who have been displaced across the Lake Chad Basin are especially vulnerable and risk abduction and recruitment by Boko Haram including for suicide bombings, he said.

“From January to June 2016, more than 50 children have been coerced to carry out suicide bombings across the four countries,” O’Brien said.

U.N. political chief Jeffrey Feltman said that despite regional efforts to weaken Boko Haram, the group continues to threaten regional stability.

He said the joint military offensive by troops from the four countries “has led to the recapture of 80 percent of areas under Boko Haram control, the freeing of thousands of captives and the prevention of terrorist attacks.”

While the military campaign is essential, Feltman said the only way to end the Boko Haram threat is for the affected countries to tackle the root causes for its emergence including addressing the social, economic and political grievances of marginalised communities.

O’Brien said humanitarian efforts to help the needy are severely underfunded, and Feltman said the military operation against Boko Haram is also facing “a severe lack of funding.” (AP)

•Photo shows Boko Haram terrorists.