"Google and Gmail will be filtered throughout the country until further notice," said Abdolsamad Khoramabadi, an Iranian official with the state-run body in charge of online censorship and computer crimes, according to the semi-official Ilna news agency. There was no indication as to whether the filtering would be temporary or permanent.
Khoramabadi claimed the decision was taken after Iranians pressed the authorities to filter the sites because of links to the film.
The Young Journalists Club, an Iranian semi-official news agency that broke the news, said the move was in reaction to YouTube's refusal to take down the anti-Islam film, Innocence of Muslims.
Despite a series of regime-sponsored protests in Tehran over the film, many Iranians appear not to be bothered by it.
At midnight in Tehran, Google was still accessible, according to citizens who spoke to the Guardian, but some said they could not access their Gmail accounts as some internet service providers appeared to have blocked the service.
"Just three hours ago I was still able to access my Gmail account but now I cannot open it," said a Tehran citizen who asked not to be named. Another citizen in the central city of Isfahan, however, said Gmail was still accessible.
The decision to filter Google and Gmail has coincided with government plans to launch the initial phases of a national internet, a countrywide network aimed at substituting services run through the world wide web.
"In recent days, all governmental agencies and offices … have been connected to the national information network," said Ali Hakim-Javadi, deputy communications and technology minister, according to the semi-official Mehr news agency.
Iran's national internet project has prompted fears among web users that authorities might be planning to pull out of the global internet, but some experts believe that they are creating it to secure the regime's own military, banking and other sensitive data from the outside world.
"Iran has fears of an outside cyber-attack like that of the Stuxnet, and is trying to protect its sensitive data from being accessible on the world wide web," an Iranian IT expert with close knowledge of the national internet project told the Guardian earlier this year. Stuxnet, a computer worm designed to sabotage Iran's uranium enrichment project, hit the country's nuclear facilities in 2010.
Many Iranian have taken to social networking websites such as Facebook and Twitter to react to Khoramabadi's announcement.
Golnaz Esfandiari, who has a blog on the Radio Free Europe website, Persian Letters, tweeted: "By blocking Gmail/Google, #Iran government punishes its own people over anti-Islam movie. Most Iranians have not seen it/don't care."
Iran is among the world's most censored countries and has widespread online censorship.
According to the New York-based the Committee to Protect Journalists (CPJ), Iran is ranked fourth in the latest list of the most censored countries, behind Eritrea, North Korea and Syria.
Access to more than 5m websites are filtered in the country, including social networking websites such as Facebook and Twitter, and the websites of many western media organisations, including the Guardian, BBC and CNN. The website of the New York Times is not blocked.
People in Iran who try to visit blocked addresses, are redirected to a web page that reads: "Access to the website is denied according to [Iran's] computer crimes regulations."Many Iranians access blocked addresses with help from proxy servers or virtual private network (VPN) services and as many as 17 million Iranians have Facebook accounts, although the site remains blocked in Iran.
Despite censorship, Iranian authorities, fearful of falling marriage rate, announced last week that they were contemplating to give permission for the country's first spouse-finding website.
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