The restrictions were announced in a mobile phone text message reportedly
from Abdolsamad Khoramabadi, an adviser to Iran's public prosecutor's office and the secretary of an official group tasked with detecting Internet content deemed illegal.
"Due to the repeated demands of the people, Google and Gmail will be filtered nationwide. They will remain filtered until further notice," the message read.
Residents in Tehran who spoke to AFP
said they were unable to get into their Gmail accounts unless they used VPN (virtual private network) software commonly used by tech-savvy Iranians to evade extensive online censorship.
Google's YouTube video-sharing site has witnessed frequent censorship since mid-2009 after elections that returned President Mahmoud Ahmadinejad to power. The opposition protested his re-election with claims of vote fraud and used YouTube to communicate to the world.
Ever since, other social networking sites, such as Facebook and Twitter, have also been routinely blocked.
The latest restrictions are reportedly part of measures to establish a domestic internet
that, reports say, would be separate from the worldwide Internet. Iran says its national intranet will be clean of un-Islamic content whilst being faster and more secure. But users' data will be more easily subject to monitoring, according to reports.
The Iranian authorities say its latest move would not amount to shutting down the Internet.
AFP reports that according to Mohammad Soleimani, a politician heading a parliamentary communication committee, “Cutting access to the Internet is not possible at all, because it would amount to imposing sanctions on ourselves, which would not be logical. However, the filtering will remain in place."