A senior United Nations official says the abject poverty and horror resulting from attacks by the extremist Boko Haram group in Africa's Lake Chad basin are at their worst and called for increased relief funding for its 3 million people and broader international engagement in the region.

Toby Lanzer, the world body's regional humanitarian coordinator for the Sahel region — of which the Lake Chad basin is a part — spoke with reporters in a briefing on Tuesday.

Lanzer said more relief money alone will only serve as a stop-gap if it is not coupled with investments in development and infrastructure.

He says the poverty in this area of northern Nigeria, Cameroon, Chad and Niger is "of the like I've hardly ever seen before."