Nigeria's President Muhammadu Buhari has said the government will avenge the attack on a UN helicopter in which two people died.

The president described the attack in the north-eastern state of Borno as "dastardly" that will not go away without "severe consequences", local media reported.

A five-year-old child is among the two who were killed in the attack on Saturday attributed to insurgents in the restive north-eastern region.

The helicopter was being used to facilitate humanitarian support to civilians in the area that has been affected by violence for more than a decade.

The UN has in the meantime halted humanitarian aid in the region.