Norway said it detained a Russian caught crossing the border in the Scandinavian nation's far north as he returned home with two drones and a cache of photos and videos.
The move comes as Norway is on high alert following several reports of mysterious drone sightings close to offshore oil and gas drilling platforms run by the major energy producer.
Last month's Nord Stream gas pipeline blasts in the Baltic Sea are widely assumed to be the result of sabotage.
The man, named as 50-year-old Vitaly Rustanov, was arrested this week at the border post of Storskog, the only transit point between Norway and Russia.
A judge at a court in Vadso ordered Rustanov to be placed in custody for two weeks in line with a police request.
"There are... reasons to believe the accused will try to escape judicial proceedings unless he is placed in provisional custody," the judge ruled.
Rustanov was carrying two Russian passports and an Israeli one when arrested attempting to drive back into Russia, he noted.
According to the judge's ruling, Rustanov had admitted flying drones "across the whole country" but denied any wrongdoing.
In Norway since August, he was carrying a partially encrypted four-terabyte stash of photos and videos when arrested.
"He has explained he was in Norway as a tourist visiting somebody," police official Anja Indbjor told the Verdens Gang daily.
"He has explained he photographed and flew a drone for private reasons and indicated he likes taking photos and is a photographer," added Indbjor.
She said that "what we have seen thus far backs up his claim to be a tourist."