Japanese police have arrested six men for alleged involvement in child pornography that possibly involved the abuse of as many as 168 boys, media reported Thursday.
The arrested were aged 20 to 66, the top-selling Yomiuri Shimbun and other media said, citing a police statement.
The victims reportedly ranged from the ages of four to 13.
Police could not immediately comment on the reports when contacted by AFP, and it was unclear from them when the arrests occurred.
But they came as Japan takes gradual steps to toughen laws against child pornography after years of criticism from international campaigners.
In 2014 the country joined other major developed nations and criminalised the possession of child pornography, not just production.
Among the detained was a tour company employee whose job involved being at camps for children, the Asahi Shimbun daily and other media reported.
The man, from Osaka prefecture in western Japan, allegedly touched and undressed children at those events when making pornographic photos and videos.
He also brought three college students who he met online as volunteers to the camps where they engaged in the alleged molestation.
The four allegedly shared pornographic images with two other men — a substitute school teacher and a retired teacher, both from Tokyo, the Yomiuri said.
The teachers, meanwhile, shared with the four pornographic images of children that they had created.
All the suspects avoided using the internet to exchange the images in an attempt to avoid cyber policing by authorities, the reports said.
Investigators found at least 100,000 movies and photos in their computers and other storage devices.