Wednesday's killings in Tehran by Iranian members of Islamic State drew a shocked response similar to that in Western countries when they too have been attacked by locally-born jihadists.
In a condolence message ahead of a funeral for the victims, Ayatollah Ali Khamenei said the attack: "will not damage the Iranian nation's determination and the obvious result is nothing except an increase in hate for the governments of the United States and their stooges in the region like Saudi (Arabia)".
The Islamic State claimed responsibility of the two attacks - a suicide bomb and gun assault.
Iran's Intelligence Ministry said Thursday that five of the men involved in the attacks were Iranians who had joined IS.
These operations took place after the National Security Ministry on Thursday published the identity of five of the suspects responsible for the Tehran attack.
Bombers and gunmen killed 17 people in Iran's parliament and near the mausoleum of the Islamic Republic's founder, Ayatollah Khomeini, on Wednesday (June 7), in rare strikes on the capital that exacerbated regional tensions. It said dozens of people have been detained.
Trump said the U.S. would "grieve and pray" for the victims, but added: "We underscore that states that sponsor terrorism risk falling victim to the evil they promote". He concludes by threatening the royal family of Saudi Arabia and promises, "after Iran, it will be your turn".
He said anti-Iranian remarks by Saudi Arabia's foreign minister and U.S. President Donald Trump are a "matter of disgrace" for them.
One senior Iranian official told Reuters that Islamic State had established a network of support in the country, and suggested that members' motivation was as much political and economic as to do with Sunni radicals' belief that Shi'ites are infidels.
Lawmakers of the Iranian Parliament were briefed on the recent deadly terror attacks in the country by the Iranian Intelligence and Interior Ministers as well as Deputy Commander of the Islamic Revolution Guard Corps (IRGC) Brigadier General Hossein Salami in a closed-door session of Parliament (Majlis) on Sunday.
The attackers were armed with rifles and pistols and at least two blew themselves up with suicide vests, Iranian media reported. He did not elaborate.