Detectives “stormed a prayer house used as a detention camp” on Wednesday evening and discovered 15 men and women aged between 19 and 50 chained by the legs, Lagos police spokesman Bala Elkana said.

The pastor of the church, “prophet” Sunday Joseph Ojo, and 10 others were arrested.

The victims “were brought by their families to seek spiritual help from mental illness and other diseases. The prophet said he has been in the healing ministry since 1986, and that he chained them in order to prevent them from escaping,” the police spokesperson added.

Some of the victims had spent five years in the church, he said, adding that further investigations will take place into the incident.

Non-governmental organisations first alerted police to Ojo’s “Blessing of Goodness Healing Church” in the Ijegun area of Nigeria’s most populous city, according to local reports.