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Iranian intelligence officials said Monday they had broken up "the biggest terrorist plot" to ever target Tehran and other provinces in the Islamic Republic, The Associated Press reported.

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, according to the news agency.

Several suspects have been arrested and are under interrogation over the plot after agents seized ammunition and bombs, state TV said.

The report didn't identify those arrested, though it called them "takfiris," a term in both Arabic and Farsi referring to Muslims who accuse others of being "nonbelievers."

Iranian authorities often refer to followers of the Sunni jihadist group Islamic State (ISIS) as "takfiris," though it isn't clear if this case involved the extremist group that holds territory in Iraq and Syria.

Shiite Iran has been helping both the Syrian and the Iraqi government in their battles against the Islamic State group. It has warned of possible attacks targeting the country, which largely hasn't seen such attacks since the immediate aftermath of its 1979 Islamic Revolution.

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 but it remains unclear whether that included the plot announced Monday by state television, noted AP.

Iran is well-known for its own backing of terrorism in other countries, mainly through its terrorist proxy Hezbollah.

A recent report by the U.S. State Department identified Iran as the world's leading sponsor of terrorism.

Iran rejected the report, calling it "false" and saying it is further evidence of the "lack of credibility of reports by the U.S. State Department."