"Some of the members are of Islamic State (IS) and the perpetrators have a history of being affiliated with Takfiri groups in Syria, Afghanistan, Pakistan and the Kurdistan region of Iraq," Iran's intelligence ministry added in a statement.
The militant group has claimed several attacks in Iran, including deadly twin bombings in 2017 that targeted Iran's parliament and the tomb of the Islamic Republic's founder, Ayatollah Ruhollah Khomeini.
More recently, IS claimed responsibility for an attack on a Shia shrine last October, where 15 people were killed in the southwestern city of Shiraz.
Source: Reuters
Comment: Gunmen storm Iranian pilgrimage site in major attack: 15 dead, 40 wounded