Iranian intelligence officials have broken up "the biggest terrorist plot" ever planned to target Tehran and other provinces in the Islamic Republic, the country's state television reported on Monday.
An anchor on state television read off a statement attributing the information to Iran's Intelligence Ministry. Officials could not be immediately reached for comment to elaborate.
Several suspects have been arrested and are under interrogation over the plot after agents seized ammunition and bombs, the state TV said.
The semi-official Fars and ISNA news agencies quoted Ali Shamkhani, the secretary of Iran's Supreme National Security Council, as saying the attack was timed to hit during the Muslim holy month of Ramadan. Iran's state-run IRNA news agency, citing the Intelligence Ministry, said the attack was supposed to come on the anniversary of the death of the Prophet Muhammad's wife, Khadija, which was commemorated in small ceremonies across Iran on Thursday.
The report didn't identify those arrested, though it called them "takfiris," a derogatory term in both Arabic and Farsi referring to Muslims who accuse others of being "nonbelievers."
Iranian authorities often refer to followers of the Sunni militant Islamic State group as "takfiris," though it isn't clear if this case involved the extremist group that holds territory in Iraq and Syria.
Shiite power Iran has been helping both the Syrian and the Iraqi government in their battles against the Islamic State group. It has warned of possible militant attacks targeting the country, which largely hasn't seen such attacks since the immediate aftermath of its 1979 Islamic Revolution.
IRNA, however, called those involved in the plot "Wahhabi takfiris." Wahhabism is an ultraconservative school of Islam practiced predominantly in Saudi Arabia.
Relations between Iran and Saudi Arabia have frayed following the kingdom's execution of a prominent Shiite cleric in January and subsequent attacks by protesters on Saudi diplomatic posts in Iran. The kingdom cut diplomatic relations with Tehran following those attacks.
Iran recently announced it would not be sending pilgrims to Saudi Arabia for the annual hajj pilgrimage, as it said the kingdom did not meet Iran's requests for better security for Iranian pilgrims. The hajj pilgrimage is required of all able-bodied Muslims once in their lifetime.
In May, Iran's Intelligence Minister Mahmoud Alavi announced that 20 "terrorist groups" that planned to detonate bombs and cause insecurity across the country had been dismantled. It's unclear whether that included the plot announced Monday by state television.
Iran faces threats from several militant groups. Last week, Iran's Revolutionary Guard battled armed members of an insurgent Kurdish group in the country's West Azerbaijan province near its border with Iraq and Turkey.
Both sides gave conflicting death tolls from the fighting, as the Guard said its forces killed 12 insurgents while three of its own died. The Democratic Party of Iranian Kurdistan said Kurds killed over 12 Guard members, including a colonel.