Military communications signals were jammed by Russia during last year's NATO exercise in Norway, according to the country’s Defence Minister.
There were reports at the time that GPS navigation systems were not working effectively.
It is now believed that interference was intentional – with Norway claiming it has evidence proving Russia was the culprit.
Exercise Trident Juncture was designed to demonstrate a NATO response to a hostile state.
Large numbers of personnel (50,000) from 31 different nations were mobilised to the high north.
Five months after the exercise took place, the evidence is mounting that the simulation was a target itself.
Now, the Norwegian government says they have evidence signals were indeed jammed by Russia.
"Russia asked us to give proof. We gave them the proof," said Norway’s Defence Minister.
"They were exercising very close to the border and they knew this will affect areas on the other side."
Russian officials are now believed to be reviewing the evidence – telling Norway’s government they will get back to them.
The best protection against interference - experts say - is ensuring the public know what to do if those systems go down, meaning that disruption is not translated into disaster.
Exercise Trident Juncture took place in areas across Norway, Sweden and Finland.
While Norway is a full NATO member, Sweden and Finland are not.
Finland also shares a 1,340 km border with Russia, and it is believed that their decision to take part in Exercise Trident Junction could have angered Moscow.
It is claimed the Kremlin decided to carry out its own exercises nearby – and allegedly interrupted signals coming from satellites in the Arctic – affecting both military and civilian navigation systems.
Commercial airlines in Finland and Norway reported disturbances at the time, but the Kremlin denied any responsibility – calling the accusations a 'fantasty'.