A "peeping Tom" who used a pen-shaped camera to take an upskirt shot of a cabin attendant during a domestic flight in Japan has avoided charges after prosecutors failed to decide which prefecture the plane was flying over at the time, reports said.

The 34-year-old man extended his hand with the micro-camera while seated and took the picture of the flight attendant, the Asahi daily said on its website on Sunday.

He was arrested by police and admitted what he had done, saying he was "aroused by uniforms," the report added.

The man was on a Japan Airlines flight from Takamatsu in the southwest of the country to Tokyo last month, according to an earlier report by Kyodo News.

The police tentatively determined the photo was taken over the western prefecture of Hyogo based on witness accounts and their analysis of flight data, it said.

But prosecutors judged they were unable to rule out the photo may have taken when the plane was over neighbouring prefectures, Kyodo added.

"Peeping Tom" offences typically fall under prefecture-level law to prevent public nuisances and their applications require prosecutors to state exact locations of the crime.

AFP