Nigerian police say they have rescued nearly 500 people from a building that houses an Islamic school where they were detained and allegedly tortured.
Those held at the facility in the northern city of Kaduna were all men and boys some were found chained up.
Kaduna state’s police chief Ali Janga told the BBC the building was raided following a tip-off about suspicious activity.
He described it as a “house of torture” and a case involving human slavery.
Some captives were as young as five years old, according to police.
The detainees, not all Nigerian, said they had been tortured, sexually abused, starved and prevented from leaving – in some cases for several years.
It is not clear how they got there. Some of the children told the police that their relatives had taken them there believing the building to be a Koranic school.
Two of the children freed by police said their parents had sent them there from Burkina Faso. Police believe the rest are mostly from northern Nigeria.
Eight suspects have been arrested, most of whom were teachers.
The police chief said the detainees some with injuries and starved of food were overjoyed to be freed.
They were taken to a stadium in Kaduna overnight to be cared for while arrangements are made to find their families.
Nigerian authorities say the nearly 500 freed captives will be given medical and psychological examinations.
Islamic schools are popular in northern Nigeria but there have long been allegations of abuse in some schools, and of pupils being made to beg for money on the streets.