The children, aged between 13 and 15, picked up the explosive device along with some scrap metal and stored it in an uncompleted building at an Islamic school in the Gubio area of Borno state, heartland of a long-running Islamist insurgency.
A spokesperson for the Gubio local government said the device had detonated and killed the six as they sought to sell it as scrap metal on Saturday.
The students at the school, which teaches children to recite the Qur'an, often collect scrap metal to sell to local communities.
Borno state police spokesperson Daso Nahum Kenneth confirmed the incident but could not immediately give any further details.
(Reporting by Ahmed Kingimi; Writing by MacDonald Dzirutwe; Editing by David Holmes)
