Norway is on high alert following 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 51 year-old Russian man, whose name was not disclosed, was arrested Friday on suspicion of flying a drone in Norway, to which he confessed.

“Police have confiscated a large amount of photography equipment, including a drone and a cache of memory cards”, police in the northern town of Tromso said in a statement.

The confiscated material included photographs of another airport in the northern town of Kirkenes and the Norwegian military’s Bell helicopters, it said.

READ ALSO: Could Norway’s gas supplies become a target for saboteurs?

Norway’s Police Security Service has been called in on the investigation, Tromso police said.

The Scandinavian country, along with several other Western nations, has forbidden Russians and Russian entities from overflying its territory following the February invasion of Ukraine.

Breaking that ban is punishable by a three-year prison term.

On Friday, Norwegian police said they had detained another Russian caught crossing the border in the far north earlier this week as he returned home with two drones and a cache of photos and videos.

That man, named as 50-year-old Vitaly Rustanov, was arrested at the border post of Storskog, the only transit point between Norway and Russia.

Rustanov admitted flying drones “across the whole country” but denied any wrongdoing, and was on Friday placed in provisional custody for two weeks.

He was carrying two Russian passports and an Israeli one when arrested attempting to drive back into Russia.

In Norway since August, he was carrying a partially encrypted four-terabyte stash of photos and videos when arrested.

With Russia’s invasion of Ukraine having led to a huge fall-off of Moscow’s energy deliveries, Norway has overtaken Russia as the main supplier of natural gas to Western Europe.

Following the Nord Stream explosions and drone sightings, Norway increased security around its energy installations.