TEHRAN, Iran (AP) -- Iran said Monday it broke up one of the "biggest terrorist plots" ever on its soil by Sunni extremists planning bombings in Tehran and elsewhere, emphasizing that the Shiite power could be facing threats at home for its military actions in Iraq and Syria.
Iran faces several low-level insurgencies, but a major militant attack hasn't struck Tehran since the years immediately following its 1979 Islamic Revolution.
That fact, coupled with authorities' suggestions the Sunni militants of the Islamic State group may be behind the plot, significantly raises the danger that Iran could face the same sectarian violence drowning Iraq and Syria, where its actions have earned the hatred of Sunni hard-liners.
"I don't think anyone should be surprised if anything like this were to happen in Iran," said Ellie Geranmayeh, a policy fellow at the European Council on Foreign Relations. "Iran has made itself a number of enemies. But so far, what has been surprising in Iran is that they've managed to contain the threat."
An Intelligence Ministry statement read on state TV and carried by local news agencies offered few details of the plot. It said authorities made arrests, seized bombs and ammunition and that investigations continued "inside and outside of the country."
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 marked Thursday in small ceremonies across Iran.
The reports didn't identify those arrested and interrogated, though it called them "takfiris," a derogatory term in both Arabic and Farsi referring to Sunnis who accuse other Muslims of being infidels. Iranian authorities and others throughout the Middle East often refer to Islamic State fighters as "takfiris."
Calls to the Intelligence Ministry rang unanswered Monday.
In Syria, Iranian troops backing embattled President Bashar Assad in his country's bloody civil war have fought Islamic State extremists and other rebel groups. Iranian casualties in the war have mounted in recent months, and the Islamic State group often mentions Iran in its propaganda messages. Iranian militias and advisers also are backing Iraq's government against IS fighters.
IRNA, however, called those involved in the plot "Wahhabi takfiris" in its Farsi report on the arrests. Wahhabism is an ultraconservative Sunni ideology practiced predominantly in Saudi Arabia that the Islamic State group has incorporated into its apocalyptic beliefs.
Mentioning Wahhabism, however, also may be an Iranian dig at Saudi Arabia. Relations between the two have frayed following the kingdom's January execution of a prominent Shiite cleric and subsequent attacks by protesters on Saudi diplomatic posts in Iran. The kingdom cut diplomatic relations with Tehran following those attacks, and now it appears that Iranians won't take part in this year's hajj, a pilgrimage required of all able-bodied Muslims once in their life.
Iran has warned of possible militant assaults targeting the country, which hasn't seen large-scale attacks since the 1980s. The worst was on June 28, 1981, when a blast at the ruling Islamic Republican Party's headquarters in Tehran killed at least 72 people, including the party's leader, four government ministers, eight deputy ministers and 23 parliament members.
Following that attack, security agencies and the Revolutionary Guard tightened their grip on security in Iran. While authorities have announced breaking up other plots, they have not described those with the same terms used Monday.
"This is coming much closer to home," Geranmayeh said. "It's in a way doubling-down on their justification for what's going on in Syria and in Iraq."
Geranmayeh said the statement's credibility also may be bolstered because it came from the Intelligence Ministry, as opposed to the Guard, a hard-line paramilitary organization that has deep suspicions of the West and exists to perpetuate Iran's Islamic form of governance and politics.
Iranian state TV previously reported the arrest of 44 people in a November sweep targeting militants, including some who wanted to join militants in Iraq and Syria. In May, Intelligence Minister Mahmoud Alavi said 20 "terrorist groups" that planned to detonate bombs and cause insecurity across Iran had been dismantled. Officials in those cases did not specifically name the Islamic State group, though it was widely believed to be involved.
Iran also faces threats from several other militant groups in the country, ranging from Sunni Arabs in its southern, oil-rich region, Kurds in its northwest and Baluch separatists on its eastern border with Pakistan.
These attacks rarely become public knowledge in Iran, though fighting last week between Kurds and Revolutionary Guard forces in West Azerbaijan province saw fatalities. A Sunni Arab group also claimed an attack on an oil pipeline in southern Iran last week, while Iranian forces battled the Sunni militant group Jaish al-Adl in its southeast, according to Stratfor, a private intelligence firm based in Austin, Texas.
"Iran still has a good handle on this spread of separatist activity, but regional competition is intensifying, and Iran has plenty of adversaries that may want to give it a taste of its own medicine," Stratfor said in an analysis published Thursday.