TEHRAN – Iran has unleashed a cyber army which draws on the ranks of Islamist volunteer militias to counter attacks online and take down "enemy websites," the official IRNA news agency reported on Monday.

"Just as we are under attack from our enemies on the web, e-trained Iranian military experts, including Basiji teachers, students and clerics, are attacking enemy sites," said Ali Fazli, deputy chief of the volunteer Islamist Basij militia, quoted by IRNA.

The admission that Tehran was engaged in cyber warfare and mass hacking gave no details on the type of attacks launched against foreign websites or on the nature of these sites.

Ultra-conservative sites have reported in recent weeks cyber attacks launched from Iran against Voice of America Farsi, Dutch government-funded Radio Zamaneh, which also broadcasts in Farsi, and microblogging site Twitter.

The general secretary of Iran's Supreme National Security Council, Saeed Jalili, said earlier that "enemies of Iran" had funded the creation of "874 websites" to destabilise the Iranian government.

The websites he referred to emerged alongside opposition-led demonstrations contesting the re-election of President Mahmoud Ahmadinejad in June 2009.

Computer experts say the crackdown on the Internet heightened after the election aimed at curbing an opposition movement that used the Internet to garner wide support against Ahmadinejad's government.

Restrictions have been tightened even more since the uprisings in the Arab world, which began in Tunisia in December, they say.

In January, Iran announced the launch of a special police unit to combat "cyber crimes", especially those committed on social networking websites such as Facebook and Twitter which are popular among the opposition and dissidents.

The Tehran government also blocks the majority of foreign news websites, accusing Western media of taking part in a plot by the United States, Israel and Britain-led Europe, against the Islamic Republic.

Iranian authorities stripped 11 correspondents, including AFP's Jay Deshmukh, of their press cards on February 15, a day after they had covered a major Tehran protest.

Hackers regularly bring down Iran's official websites, while its nuclear facilities were targeted by the so-called Stuxnet worm, aimed at the gas centrifuges used to enrich uranium in defiance of international sanctions.

Fingers were pointed at Israel or the United States as the developers of Stuxnet, which one computer expert described as "a cyber weapon of mass destruction."

In November Ahmadinejad admitted that uranium enrichment had suffered problems caused by malware, in an apparent reference to Stuxnet, but said the issues had been resolved.