So it’s official state tv said Sunni groups involved in this. Sad to see Muslim are killing Muslims .
RIP. .... Arrest them irrespective of any religion and hang them.
We should not tolerate terrorism & extremism in any form by any group.
Iranian soldiers taking cover in a rain gutter at the scene of an attack on a military parade in the southwestern city of Ahvaz on September 22, 2018. AFP
"The response of the Islamic Republic of Iran to the smallest threat will be crushing," Rouhani said on his official website. "Those who give intelligence and propaganda support to these terrorists must answer for it." Foreign Minister Mohammad Javad Zarif said in a tweet that the attack near the Iraqi border was carried out by "terrorists recruited, trained, armed & paid by a foreign regime".
"Iran holds regional sponsors and their US masters accountable for such attacks," he wrote.
IS jihadists said via their propaganda mouthpiece Amaq that "Islamic State fighters attacked a gathering of Iranian forces" in Ahvaz.
The city lies in Khuzestan, a province bordering Iraq that has a large ethnic Arab community and has seen separatist violence in the past that Iran has blamed on its regional rivals.
State television gave a casualty toll of 29 dead and 57 wounded.
Armed forces spokesman Brigadier General Abolfazl Shekarchi said the dead included a young girl and a former serviceman in a wheelchair.
"Of the four terrorists, three were sent to hell at the scene, while the fourth who had been wounded and arrested went to hell moments ago due to his severe wounds," Shekarchi told state television.
Khuzestan deputy governor Ali-Hossein Hosseinzadeh told the semi-official ISNA news agency that "eight to nine" troops were among those killed, as well as a journalist.
"Those who opened fire on civilians and the armed forces have links to the Ahvazi movement," Guards spokesman Ramezan Sharif told ISNA.
In a message of condolence to Russia's close regional ally, President Vladimir Putin said he was "appalled by this bloody crime".
In a keynote speech, Rouhani vowed to boost Iran's ballistic missile capabilities despite Western concerns that were cited by his US counterpart Donald Trump in May when he abandoned a landmark nuclear deal with Tehran.
"We will never decrease our defensive capabilities... we will increase them day by day," Rouhani said at a military parade. "The fact that the missiles anger you shows they are our most effective weapons," he said, referring to the West.
Iran has ballistic missiles with a range of up to 3,500 kilometres, enough to reach bases in the Middle East, Africa, Eastern Europe and Indian Continent.