Long queues have formed outside petrol stations, angering motorists in a country already suffering under tough economic sanctions over its nuclear dispute with major powers.

"Guys, can you tell me where we can get gasoline in the east, northeast or even north of Tehran?" one user asked on Twitter.

Of Iran's 4,300 petrol stations connected to the system, only 220 had been reconnected, Fatemeh Kahi, a spokeswoman for the National Oil Products Distribution Company, told the official IRNA news agency Wednesday.

However, she added, "nearly 3,000 stations can distribute fuel offline, but at the open price" -- the rate consumers must pay once they have used up their monthly allowance of subsidised fuel.

The conservative Fars news agency on Tuesday linked the breakdown to opponents ahead of the second anniversary of deadly protests sparked by a hike in petrol prices.

Fars reported that "a campaign carried out by counter-revolutionary media" ahead of the November 15, 2019 anniversary "reinforces the possibility of a cyber attack."

On that date two years ago the announcement of a sudden increase in fuel prices triggered protests in dozens of locations across the country.

It was Iran's most vocal eruption of public dissent in a decade.