Iran's supreme leader on Monday said the attackers who killed 24 people at a military parade in the southwestern city of Ahvaz were funded by Saudi Arabia and the United Arab Emirates.
"Based on reports, this cowardly act was the work of those very individuals who are rescued by the Americans whenever they are in trouble in Iraq and Syria and who are funded by the Saudis and the (United) Arab Emirates," Ayatollah Ali Khamenei said, in remarks posted on his official website.
He did not give any further details on the identity of those behind what he called a "terrorist attack".
In the immediate aftermath of the attack on Saturday, Iranian authorities said they suspected Arab separatist groups were behind the attack, none of whom is known to have a presence in Syria.
Khamenei, who was speaking to a group of Iranian athletes, said the attack "once again shows the Iranian nation faces many enemies on its proud path of progress and development".
"We will most certainly rigorously punish the perpetrators of this attack," he added.