Iranian Intelligence Minister Mahmoud Alavi announced on Monday that the most of those persons behind the Saturday terrorist attack in Ahvaz have been arrested.
"We will bring to justice each one of the terrorists", Alawi said, addressing the funeral procession of the martyrs of the terror attack held in Ahvaz on Monday morning.
The father of 4-year-old victim Mohammad Taha lay atop his son's flag-draped coffin sobbing, a public display of grief near the Sarallah Mosque in Ahvaz, the capital of Iran's oil-rich province of Khuzestan.
"Based on reports, this cowardly act was done by people who the Americans come to help when they are trapped in Syria and Iraq, and are paid by Saudi Arabia and the UAE", Khamenei was quoted as saying on his official website.
In his address, IRGC deputy head Hossein Salami reiterated accusations against the United States and Israel and warned the two countries to expect a "crushing and devastating" response from Tehran.
"As you can see now, all of the people, whether they're Lor, Arab, Shushtari or Dezfuli, are all here today and all say death to the terrorists", he told AFP.
Iranian women hold images of one of the victims during a public funeral ceremony for those killed during an attack on a military parade on the weekend, in the southwestern Iranian city of Ahvaz on September 24, 2018.
The men appear to be dressed in Revolutionary Guards uniforms and talk about the importance of jihad.
The attack, one of the worst against the most powerful military force of the Islamic Republic, struck a blow at its security establishment at a time when the United States and its Gulf allies are working to isolate Tehran. He adds: 'We will destroy them with a strong and guerrilla-style attack, inshallah (God willing)'.More news: Paul Pogba: Alexis Sanchez will deliver at Manchester United
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"Iran's answer (to this attack) is forthcoming within the framework of law and our national interests", said Mr Rouhani, adding that the U.S. would regret its "aggressiveness".
"We are Muslims, they are kafirs (non-believers)", the man reportedly could be heard saying.
President Hassan Rouhani has accused a US -allied regional country of supporting the perpetrators.
Senior commanders of the Islamic Revolutionary Guards Corps (IRGC) have said the Ahvaz attack was carried out by militants trained by Gulf states and Israel, and backed by America.
It is, however, highly unlikely the Guards will strike any of its foes directly and risk sparking a regional conflict.
Iran's Fars news agency said on Monday that five attackers were killed in the attack, not four as previously reported by state media.
Rouhani engineered Iran's 2015 nuclear deal with world powers that ushered in a cautious detente with Washington before tensions flared anew with Trump's decision in May to pull out of the accord and reimpose sanctions on Tehran.
Iran is at odds with Western-allied Gulf country Saudi Arabia for predominance in the Middle East.
The Iranian Students' New Agency reported that authorities killed three attackers on site and another died of his injuries at a hospital.