Iran has "arrested or summoned" around 450 social media users over their online activities, a website linked to the powerful Revolutionary Guards said on Tuesday.
Gherdab, the cyber arm of the Guards, said the people targeted administered pages on social networks including smartphone applications such as Instagram, Telegram and WhatsApp.
“These people were carrying out immoral activities, insulted religious beliefs or had illegal activities in the field of fashion,” said Gherdab.
It said the suspects would be put on trial without specifying how many exactly have been placed under arrest.
Isna news agency carried a similar report.
Iranian authorities have for years tried to impose curbs on its citizens using social media.
Facebook and Twitter are officially banned in the Islamic republic, although users can gain access with easily available and cheap software.
But applications such as Instagram, Telegram and WhatsApp are available to Iranians and very popular.
More than half of Iran’s population of 80 million is online, with Telegram, an instant messaging app alone having more than 20 million users.
President Hassan Rouhani, a moderate, has repeatedly pointed to the ineffectiveness of measures to limit access to social media.
In May, state news agency IRNA reported that a committee headed by Rouhani had set a one-year deadline for foreign social media to hand over data on their Iranian users.
That same month, the head of Tehran’s cybercrimes court said on state television that authorities had arrested eight people for working in “un-Islamic” online modelling networks, particularly on Instagram.