"We are aware of reports of an attack by gunmen on an Iranian military parade in Ahvaz. We stand with the Iranian people against the scourge of radical Islamic terrorism and express our sympathy to them at this terrible time. The United States condemns all acts of terrorism and the loss of any innocent lives," Nauert said.
Previously, Iran summoned ambassadors of the United Kingdom, Netherlands and Denmark, accusing the countries of harbouring Iranian opposition groups, according to Iran's Islamic Republic News Agency.
Meanwhile, Iranian Armed Forces spokesman, Brig. Gen. Abolfazl Shekarchi said after the attack that the militants who had committed it were linked to the United States and Israel. Iranian Foreign Minister Javad Zarif had also accused "regional terror sponsors and their US masters" of organizing the attack.