Intelligence Minister Mahmoud Alavi in a televised interview with IRIB on Saturday said the mastermind and main commander of terrorist attacks on Iran's parliament and the shrine of Ayatollah Khomeini on June 7 had been situated in border areas and fled the country after the operation was crushed and all perpetrators killed.
The country's Supreme Leader said the attacks will add to the hatred that Iranians harbor toward the USA and Saudi Arabia.
"Exactly when the Iranian people was engaged with an attack on the parliament by terrorists, the US Senate shamelessly approved a bill against the Iranian people, and approved supporting terrorists", he said.
Thousands packed Tehran's streets on Friday to mourn the victims of two suicide bomb and gun attacks, and joined their supreme leader in accusing regional rival Saudi Arabia of involvement in the assaults.
While ISIS claimed responsibility, Iranian officials have also suggested Saudi Arabia may have played a role - and Iran's foreign minister called the official USA 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".
L'Antica Farmacia nei Piccoli Musei. Evento il 18 giugno
Per consentire una migliore fruizione e in ottemperanza alle norme di sicurezza, l'ingresso sarà permesso a gruppi di 20 persone massimo per volta.
Let there be no doubt that we will take revenge for today's attacks in Tehran, on terrorists, their affiliates and their supporters, he said, as cited by the news agency Mehr. The four-minute video shows three masked men sitting on a floor holding automatic rifles.
The speaker claims to represent the "first battalion" of IS formed inside of Iran.
Irans Revolutionary Guards have accused Saudi Arabia of masterminding the deadly attacks in Tehran on Wednesday, a claim which Riyadh has denied. He speaks out at length against Shiites and promises further attacks. He further said Washington has showed that it is the global ISIL.
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 fact that Islamic State has claimed responsibility proves that they were involved in the brutal attack", said the statement, as quoted by Reuters.
A local official at the port town of Jask, also in Hormuzgan, said five suspects linked to Islamic State were detained on Monday, Iran's Mizan news agency reported.