Its nuclear chief said Iran would start enriching uranium to 20% from Tuesday, and that 10 new uranium enrichment plants would be built in the next year.
Ali Akbar Salehi said the enrichment would take place at Natanz, Iran's main uranium enrichment plant.
The move heightens fears Iran is moving closer to weapons-grade uranium.
It comes amid growing tension with the West, which has criticised Iran for stalling on a deal over its enrichment programme.
The latest development comes days before Iran celebrates the 31st anniversary of the Islamic revolution, which is expected to see pro- and anti-government demonstrations.
Almost by the day, Iran is stepping up the pace of its nuclear confrontation with the West, says the BBC's Tehran correspondent, Jon Leyne.
But if the aim is to have all 10 new plants running in a year, then it is almost laughably ambitious as it has taken many years to get Natanz, the first plant, running and it still has problems, he adds.
This flurry of announcements reflects the turmoil faced by President Ahmadinejad's government ahead of the anniversary, our correspondent says.
Witnesses say the situation in the Iranian capital Tehran is increasingly tense, with a series of checkpoints already set up across the city.
