Nigeria launched a crackdown on illegal religious schools and rehabilitation centres in late September. Nearly 1,500 people have been rescued since September.
Nigerian police have freed 259 people from a so-called Islamic rehabilitation centre in the southwestern city of Ibadan, police said on Tuesday, taking the number rescued from abusive institutions since September to nearly 1,500.
Images from local TV station TVC taken after the captives were released showed a group of mostly young men and teenage boys. Many were emaciated. An infant was also among the group.
"We eat one meal a day," freed captive Olalekan Ayoola, told TVC, saying the food wasn't fit for a dog to eat.
Nigeria launched a crackdown on the illegal schools and rehabilitation centres in late September after a man was refused permission to see his nephews at one institution and complained to police.
Many captives have said they were physically and sexually abused and chained up to prevent them from escaping.
Other sites raided in major police operations have been in the mostly Muslim north of the country. Ibadan is in the southwestern state of Oyo, which is predominantly Christian.
Oyo state police spokesman Fadeyi Olugbenga said the facility was raided on Monday at about 1300 GMT.
"Yesterday, 259 persons were released. We had women, men and teenagers," Olugbenga said. Some people were locked inside a building and some were chained.
Olugbenga said nine people, including the owner of the centre had been arrested and were under investigation.
Oyo's commissioner of police, Shina Olukolu, told reporters on Monday that anyone found culpable would be prosecuted to "serve as a warning to others who may want to operate such houses that serve as illegal detention centres".
Spokesmen for President Muhammadu Buhari, who ordered the crackdown, and the vice president both declined to comment.
The president's office issued a statement in October that said: "No responsible democratic government would tolerate the existence of the torture chambers and physical abuses of inmates in the name of rehabilitation of the victims."
Religious schools, known as Almajiris, are common across the north of the West African country. Such schools have been dogged by allegations of abuse and accusations that some children have been forced to beg on the streets.
At other raided facilities, some parents thought their children were there to be educated and even paid tuition fees. Others sent misbehaving relatives to the institutions to instil discipline.
Muftau Adamu told TVC his parents came to collect him from the centre in Ibadan but were told they must pay $3,270 first - and never came back.