"One of the biggest takfiri-Wahhabi terrorist plots was discovered and foiled," the official IRNA news agency quoted the ministry as saying, using terms applied by Iran to Sunni extremist groups.
"A series of bomb attacks prepared in various areas deep inside the country and especially in Tehran and some other provinces... Were foiled, the terrorists were arrested and a number of ready-made bombs were recovered," it said.
No more details were provided. The ministry said more information would come following investigations "both inside and outside the country."
Iran, the predominant Shiite power, has been helping both the governments of Iraq and President Bashar al-Assad's regime in Syria to battle the Sunni extremist Islamic State group.
Iranian cities have not however faced any serious threat of jihadist attack.
An increased police presence in Tehran in November and December - with armed security forces guarding subway stations and other public areas in Tehran - raised concerns that an attack was possible.
But the capital's police chief, Hossein Sajedinia, said the presence was only part of "counter-terrorism drills".
The elite Revolutionary Guards killed 12 Kurdish rebels in fighting near the Iraqi border on Wednesday that also left three members of the Guards dead.
Police said the rebels were members of the Party of Free Life of Kurdistan (PJAK), an Iranian Kurdish group with close links to Turkey's outlawed Kurdistan Workers' Party (PKK).
The same day, state television reported that a police officer and five members of Sunni militant group Jaish-ul Adl had been killed in clashes in the southeastern Sistan-Baluchistan province.