Pakistani police discovered drug addicts held in chains at an Islamic seminary that offered rehabilitation services, and said Tuesday that young children were also sometimes shackled at the institution.

The parents of around 60 young men at the seminary in the southern port city of Karachi paid it to treat their children through a regime of Islamic instruction and worship, or simply to take them off their hands.

"They were kept there like animals," said police officer Akram Naeem.

Naeem said officers had ruled out any possibility that the seminary had links with Islamist militant groups.

Patients who tried to escape or were dealing drugs were chained together, Naeem said.

Some children as young as eight were also taking regular Islamic instruction at the seminary, said policeman Rao Anwar Ahmed. He said they too were sometimes chained, if they were disobedient.

Police arrested an administrator at the complex during the raid Monday night, which was reportedly due to a tip off.

There is little or no state help for drug addicts in Pakistan, and other seminaries in the country offer similar treatment. Addicts and some mental patients are also chained at institutions around the country and in other developing nations.

Pakistan has thousands of unregulated seminaries offering free or cheap education, food and lodging for poor children.

Reports of abuse at such centers occasionally surface.

Video footage taken after the raid showed men in chains and the grubby basement room where they were held, along with bedding. The men had no obvious signs of mistreatment.

Several parents, who paid the seminary around $150 to take their children, protested the raid at a local police station.

"I brought my grown up son here because he is a drug addict and he was making my life miserable," one told a local television station. "I don't want to take him back."