"The German national was detained while taking photos of Aghajari oilfield in Khuzestan province," the report said, without elaborating.
The Iranian judiciary had yet to comment on the report.
Iran, which has been at odds with Western powers including Germany over what it calls their interference in its internal matters during months of anti-government protests sparked by the death in custody of a young Iranian-Kurdish woman in September.
The Islamic Republic has accused Western countries, Israel and Saudi Arabia of fomenting the unrest. Its allegations have been accompanied by arrests of dozens of dual-nationals and foreigners.
(Reporting by Elwely ElwellyEditing by David Goodman)
