While ISIS claimed responsibility, Iranian officials have also suggested Saudi Arabia may have played a role - and Iran's foreign minister called the official US response "repugnant", after President Trump ended his expression of condolences for the victims with the message that "states that sponsor terrorism risk falling victim to the evil they promote".
He added: "The US must know that the Islamic Republic will not back down from positions such as battling oppression and defending Palestine and will spare no efforts towards defending the people's rights". The attackers had entered Iran at some point previous year, the ministry said without providing precise dates.
Iran's powerful Revolutionary Guards Corps blamed the assault on regional rival Saudi Arabia and has threatened revenge.
Khamenei said Iran had no intention of normalising ties with the United States."The American government is against an independent Iran".
This is not the first time Saudi would be facing the ISIS, earlier, the terror outfit attacked security forces of Saudi and bombings, shootings that target the kingdom's Shi'ites.
Baqeri expressed confidence that the hegemonic system and Zionism, which have dispatched terrorists nurtured by spy agencies to Iran in cooperation with reactionary regimes in the region, would face no other fate but defeat and disgrace.Both would indicate a degree of instability and tensions that the Iranian leadership would rather not acknowledge.
On Friday Iran's supreme leader, Ayatollah Ali Khamenei said the attacks would only increase Tehran's hatred against the U.S. and its stooges, including Saudi Arabia. "Young unemployed men can be wooed and recruited".
IS has claimed responsibility for this weeks twin attack in Tehran.
Iranian police say they have arrested several suspects in their investigation into the attacks on parliament and the tomb of Ayatollah Ruhollah Khomeini, who led the 1979 revolution against the US -backed shah and is considered the founder of the Islamic republic.