The Chinese man, whose name has not been disclosed, reportedly attempted to film a royal tomb in southern Seoul last Saturday, driven by his interest in UNESCO World Heritage sites and other Buddhist temples.
Police believe he accidentally filmed the NIS headquarters in the process.
"The man was released last night after the preliminary investigation revealed no specific charges," police said. However, they added that he will be questioned further.
The man, who rented a car upon his arrival in Seoul, headed directly to the royal tomb on that day.
He is currently banned from leaving the country.
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