Kidnappers have seized more than 1,000 students and staff in raids on schools in northern Nigeria since December.

Police say vigilantes helped rescue 84 children after Nigeria's second mass kidnapping in eight days.

Pictures show the schoolboys arriving in Katsina city, a week after they were kidnapped by militants.

Militant activity is spreading across northern Nigeria with other groups expressing allegiance to Boko Haram.

Footage appears to show jihadists guarding the boys, one of whom is made to issue demands.

The Islamist militant group's leader Abubakar Shekau says it opposes Western education.

Gunmen raided an all-boys boarding school on Friday, abducting an unknown number of children.

Hundreds of students are feared missing after gunmen raided a secondary school in north-western Nigeria.