Gunmen have opened fire during an Iranian military parade in the south-western city of Ahvaz, killing several people, including civilians, and injuring at least 20, state media say.
The attackers shot from a park near the parade and were wearing military uniforms, reports say.
State media say Islamist militants are thought to be behind the attack.
Iran is marking the anniversary of the beginning of the 1980-88 war with Iraq with several parades across the nation.
Fars news agency said the attack started at 09:00 local time (06:30 BST) and appeared to involve at least two gunmen.
The attackers fired at civilians and attempted to attack military officials on the podium, Fars reports.
Pictures from the scene show wounded soldiers being taken to safety.
The shooting lasted for about 10 minutes, but security forces are now in control of the situation, state media says.
Ahvaz was one of the cities that saw large anti-government protests over falling living standards late last year.