Hope of employment more than religious belief is driving people to join fast-growing extremist groups in sub-Saharan Africa, according to a report by the U.N. Development Programme (UNDP) based on interviews with hundreds of former fighters.

While worldwide deaths from terrorism have declined in the last five years, deaths in sub-Saharan Africa have risen, making it now the global epicentre of attacks, the UNDP report said, citing an annual survey called the Global Terrorism Index.

Countries from east to west Africa have seen Islamist militant groups take over large swathes of territory, displacing millions, eroding faith in democratic government and causing widespread hunger.

The Sahel region has been the most affected, as groups linked to al Qaeda and Islamic State expand their attacks in one of the world’s poorest regions.

The UNDP report found that 25% of voluntary recruits to such groups cited job opportunities as their primary reason for joining, while 22% cited wanting to join with family and friends and 17% cited religious ideas.