AGENCE FRANCE-PRESSE in Washington

Iran has among the strictest internet censorship in the world, blocking access to sexual content, political websites, information on women's rights and "blogs", a study by internet researchers showed on Tuesday.

The OpenNet Initiative, a partnership of researchers from Harvard University, the University of Toronto and University of Cambridge, noted that Iran uses technology from the United States company, Secure Computing, calling the firm "complicit" in the censorship. But they said that internet content controls "have support at the highest levels of the Iranian state".

The researchers found that about 34 per cent of tested websites were blocked.

"The Iranian state has effectively blocked access of its citizens to many pornographic online sites, most anonymiser tools, a large number of sites with gay and lesbian content, some politically sensitive sites, women's rights sites, and certain targeted web logs [blogs], among other types of sites," the researchers wrote.

The study found online content in the Farsi language was more likely to be blocked than comparable content in English.

"Iran has put in place one of the world's most extensive and sophisticated internet censorship regimes," said John Palfrey, executive director of the Berkman Centre for Internet and Society at Harvard.

"Along with China, Iran has committed to adapting its filtering practices with changes in internet technology, which suggests that the cat and mouse game between those who would speak freely and those who would stop them is bound to continue. Bloggers who write in Farsi in Iran have a much harder job today in trying to reach their audience than bloggers in most other parts of the world."

The director of the Citizen Lab at the University of Toronto Ronald Deibert said: "Our report on Iranian filtering of the internet shows that not only are freedom of speech and access to information under threat, but that there is a growing commercial market for the technologies that diminish them.

"By providing filtering systems to non-democratic regimes, the US company, Secure Computing, is complicit in Iranian breaches of the United Nations Declaration of Human Rights. This thriving internet censorship market - spread like a virus from China to Iran to an increasing number of countries worldwide - calls into question not only the trumpeted slogans of hi-tech firms that the internet represents 'freedom' and 'connectivity', but simplistic divisions between 'us' and 'them' as well."