"At 11:44 (0814 GMT) a distributed denial-of-service attack disrupted the internet services of some mobile and fixed operators for an hour," tweeted Sajad Bonabi.
A DDoS attack involves overwhelming a target's servers by making a massive number of junk requests.
"Connections have returned to normal following the intervention of Dejfa shield," Bonabi added, referring to Iran's so-called digital fortress against cyberattacks.
He did not elaborate on the source of the attack.
Bonabi is a board member at the ministry's Telecommunications Infrastructure Company, the sole provider of the country's telecommunications infrastructure.
Internet monitor NetBlocks confirmed Saturday's outage and said it was "consistent with a targeted disruption and no technical faults are evident at the present time".
Iran said in December it had thwarted a "highly organised cyberattack" targeting its e-government infrastructure.
Telecommunication Minister Mohammad Javad Azari Jahromi described the attack as "really massive" and "state-sponsored".
In late September, the country's energy sector was put "on full alert" to the threat of "physical and cyber" attacks a few days after Iran denied media reports its oil installations had been disrupted by a cyberattack.
Iranian authorities imposed a near-total internet blackout in mid-November when street violence broke out during demonstrations against a surprise decision to hike petrol prices.
The outage stemmed the flow of videos shared on social media of demonstrations or associated acts of violence.
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