Four of the suspects took clandestine intimate photographs and videos, many in public spaces such as bus stations and shopping malls, before sharing them in a group with nearly 9,000 members, police alleged.

The suspects distributed around 15,000 such images over the course of three years, police said, charging users for "VIP" content to make HK$4 million (US$512,000).

The online platform, which was not identified, has been blocked and more arrests are possible, police warned.

"Every user who downloads these images is also an accomplice," police clinical psychologist Fung Ho-kin said.

Hundreds of women were targeted, including 200 students.

"The victims will suffer varying degrees of mental trauma," Fung said.

The suspects are aged from 20 to 62 and have been charged with a range of offences, including conspiracy to "publish intimate images without consent".