"The billboard was installed in Shiraz showing three male soldiers standing on a rocky outcrop" next to a quote from an epic Persian poem, Tasnim wrote.

But the shot was actually a photoshopped picture of Israel Defense Forces, according to Tasnim, with a female soldier from the original picture having been cropped out.

The banner was pulled down from the southwestern city Wednesday night and the mayor issued an apology the next day.

"This mistake of putting up such a despicable banner during the sacred defence week is unforgivable," Tasnim quoted mayor Heydar Eskandarpour as saying.

Iran commonly refers to the brutal eight-year war with Iraq as "the sacred defence". In recent days, the country has been marking the start of the conflict which began on September 22, 1980. Two million people died.

"In addition to apologising to Shiraz's pious and noble people, I ask the authorities to investigate the roots of this suspicious act and promptly report to the people," the mayor added.

Two public relation officials at the municipality were later fired on Thursday night, according to conservative news agency Fars.

Iranian social media was abuzz with heated reactions to the controversy.

"M16 guns, straps, clothes, helmets: all clearly belong to Zionists. The best I can say is that you did something idiotic," wrote a Twitter user identified as @mhrezaa.

Another Iranian user @masoudasadi67 also called for the swift punishment of "those who committed such a heinous act."