Iran has blocked access to more than five million internet sites because they are "immoral and anti-social", according to reports.
Internet service providers have been told over the years to block access to political, human rights and women's sites, as well as anything deemed pornographic or anti-Islamic.
The country's 21 million internet users will now also be prevented from viewing weblogs expressing dissent, along with popular sites as Facebook and YouTube.
Abdolsamad Khoram Abadi, an advisor to Iran's prosecutor general, was quoted as saying: "The enemies seek to assault our religious identity by exploiting the internet.