Updated

The head of the United Nations food agency says the collapse of the Islamic State group's self-described caliphate across Syria and Iraq has led to extremists mounting a recruitment drive in sub-Sahara Africa that threatens to trigger a new European migrant crisis.

World Food Program executive director David Beasley told The Associated Press on Monday that many of the militants who fled Syria had ended up in the greater Sahel region, a belt of semi-arid land spanning east-west across the continent and home to 500 million people.

Beasley says Islamic State militants are collaborating with other extremist groups to create "extraordinary difficulties" across Sahel.

Beasley has warned European leaders that they could face a far larger migrant crisis from Sahel than the Syrian conflict.