Islamist fighters from Nigeria's Boko Haram group have abducted more than 1,000 children in the northeast since 2013, the United Nations children's agency UNICEF said Friday.

The militants regularly took youngsters to spread fear and show power, the agency said on the eve of the fourth anniversary of the abduction of 276 schoolgirls from the town of Chibok, a case that triggered global outrage.

"Children in northeastern Nigeria continue to come under attack at a shocking scale," said Mohamed Malick Fall, UNICEF's Nigeria head.