On two occasions in May, Bornholm and southern Sweden were affected by unusually long-lasting GPS disruptions, according to Dagbladet Information.
Experts have previously pointed to Russia as responsible for the disruptions in satellite navigation that have become more frequent around the Baltic Sea and are seen as part of the Russian hybrid warfare.
The disruptions, known as jamming, lasted for eleven and six hours, respectively, reports Dagbladet Information, citing several reference stations.
It is remarkable that they were not short outages. It was something that went on for several hours throughout the night, says Søren Reime Larsen, researcher at DTU Space, to the newspaper.
He estimates that the GPS disruption originated from one or more vessels in the waters between Bornholm and Sweden.
The Danish Defence Intelligence Service (FE) declines to comment on the reports, referring to an analysis stating that disruptions over the Baltic Sea have increased since December and that it is "very likely" that Russia is behind it, writes the news agency Ritzau.