© Getty A student surfing the internet in Tehran.
Reza Taghipour, the country's telecommunications minister, said the step was being taken because sensitive intelligence was vulnerable on the worldwide web, which he said was untrustworthy because it was controlled by "one or two" countries hostile to Iran.
"The establishment of the national intelligence network will create a situation where the precious intelligence of the country won't be accessible to these powers," Mr Taghipour told a conference on Sunday at Tehran's Amir Kabir University.
He described the move as the first phase of a project to replace the global internet with a domestic intranet system scheduled to be completed within 18 months.
Opponents have previously denounced the plan as a means of stamping out western influence on the internet while further tightening already stringent online surveillance of political activists and regime critics.
While Iranian officials have repeatedly spoken about creating their own alternative to the internet, the latest announcement follows the upheaval wreaked by Stuxnet and Flame, both of which are believed to have been developed jointly by the US and Israel.
Stuxnet, discovered in 2010, caused extensive damage to Iran's uranium enrichment programme, which Iran insists is peaceful despite the west's suspicions that it is designed to produce an atomic bomb.
Flame, detected this year, was an even more sophisticated virus that is believed to have targeted Iran's oil ministry and main export terminal.
Nima Rashedan, an Iranian cyber-security specialist based in the Czech Republic, said the domestic network was unlikely to be effective. "In terms of cyber security, Iran is one of the most backward countries I know," he said. "Because of the dis-functionality of the government, I don't think they will be able to implement it properly.
They are just thinking of this now? Reminds me of Syria. Did that regime seriously think the forces of darkness would leave them in safe harbor as the storms pounded all around them? That's rather naive, and if Iran thinks they have 18 months to secure their systems, then at least they will have each other to keep company.