Iranian authorities say they have detained 27 members of a "terrorist network" suspected of planning attacks to coincide with the Islamic fasting month of Ramadan.
The group plotted to carry out "terrorist operations" in Tehran and other major cities in the country, the Intelligence Ministry said in a statement posted on its website on June 11.
The statement said the suspects "published pictures in cyberspace threatening the honorable nation of Iran with revenge and murder."
It added that the attacks were due to take place last week during the Ramadan celebration of Al-Qadr and on Jerusalem Day, marked each year to show support for Palestinians and opposition against Israel.
A large number of weapons and ammunition were confiscated, the ministry also said.
The announcement came a day after Iran's Islamic Revolutionary Guards Corps (IRGC) said they had fought off three attempts by "terrorist groups" to infiltrate from neighboring Iraq in recent days, leaving 13 attackers dead.
Iran has been targeted by Sunni extremists who see the country's Shi'ite majority as apostates. Iran has also been directly involved in the fight against the Islamic State (IS) extremist group and Al-Qaeda in both Iraq and Syria.
In June 2017, terrorist attacks claimed by the IS group killed 18 people at the parliament building in Tehran and Ayatollah Ruhollah Khomeini's mausoleum south of the capital.