Five of the men who launched an attack in the heart of Iran's capital previously fought for the Islamic State group, the country's Intelligence Ministry said yesterday, acknowledging the first such assault by the extremists in the Shiite power.
The attacks on Wednesday on Iran's parliament and the tomb of its revolutionary leader killed at least 16 people and wounded over 40, stunning its people.
The ministry issued a statement on its website with bloody pictures of the men's corpses. It identified them only by their first names, saying they did not want to release their last names due to security and privacy concerns for their families.
It described them as "long affiliated with the Wahhabi," an ultraconservative form of Sunni Islam practiced in Saudi Arabia.
However, it stopped short of directly blaming the kingdom for the attack, though many in the country expressed suspicion Iran's regional rival had a hand in it.
The men had left Iran to fight for the extremist group in Mosul, Iraq, as well as Raqqa, Syria - the group's de fact capital, the ministry said.
It said they returned to Iran in August under the command of an Islamic State leader and escaped when authorities initially broke up their extremist cell.
The ministry did not identify the men's hometowns, nor say how they were able to evade authorities.
Commuters in the Iranian capital noticed police on street corners and motorcycles, more than usual as dawn broke yesterday.
That came after Mohammad Hossein Zolfaghari, a deputy Interior Minister, told state TV that "law enforcement activities may increase."
The attack, which came as lawmakers held a session in parliament and at the shrine of Ayatollah Ruhollah Khomeini, shocked Iranians who so far had avoided the chaos that has followed the Islamic State group's rise in Syria and Iraq.
Iranian forces are backing embattled Syrian President Bashar Assad while the Shiite power also is supporting militias fighting against the extremists in Iraq.