Nigerian police say they have rescued 15 people kept chained in an illegal so-called prayer house in the country's biggest city, Lagos.

The victims were men and women between 19 and 50 years old. Some said they had spent five years in the facility.

They were brought there by relatives who believed the spiritual treatment could help cure their mental illnesses, drug addictions and other conditions.

The man who ran the facility, and called himself a prophet, was arrested.

The 58-year-old told police he had been running what he described as a healing ministry since 1986 and that the people had been chained to prevent them from escaping.

"Police are working closely with other agencies of government to provide adequate medical attention and shelter to the victims," police spokesman Bala Elkana said.

The police raided the house in the area of Ijegun after receiving a tip-off.

This is the latest raid on such privately run facilities, where people are often kept in deplorable conditions, the BBC's Mayeni Jones in Lagos reports.