US military helicopters habitually and on numerous occasions circled for hours over the site of the Nord Stream pipelines incident near Bornholm Island earlier in September, Flightradar24 data showed.

Earlier this month, a US Navy Sikorsky MH-60R Seahawk helicopter spent hours loitering over the location of the damaged natural gas pipelines in the Baltic Sea near Bornholm for several days in a row, September 1, 2, and 3, in particular.

Denmark's maritime traffic agency and Sweden's Maritime Authority on Monday reported a "dangerous" gas leak in the Baltic Sea close to the route of the inactive Nord Stream 2 pipeline, which experienced an unexplained drop in pressure.

The leak, southeast of the Danish island of Bornholm, "is dangerous for maritime traffic" and "navigation is prohibited within a five nautical mile radius of the reported position," the agency warned in a notice to ships.

Following the incident, German newspaper Tagesspiegel claimed Monday that Berlin is convinced that the loss of pressure in the three natural gas pipelines between Russia and Germany was not a coincidence and suspects a "targeted attack".

The cause of the incidents remains unknown and an investigation is underway. Swedish Foreign Minister Ann Linde said on Tuesday that the disruption was caused by detonations, which indicates that it was sabotage.

The Nord Stream 2 pipeline, which runs parallel to Nord Stream 1 and was intended to double the capacity for undersea gas imports from Russia, was blocked by Berlin in the days before the start of the war in Ukraine.

Flightradar24 showed an unidentified aircraft that did not even have a helicopter icon hovering over the site. However, the aircraft's 24-bit ICAO code included in the description makes it possible to establish the model, which is the US military's Sikorsky MH-60R Seahawk. The code is verified through open resources that collect data on military aircraft.

The US helicopter is also shown by the aircraft tracking service to have flown into the area of loitering over the Nord Stream pipelines from Gdansk, Poland.

On the second day of the loitering, almost in parallel with their US counterpart, a Dutch navy NH9 helicopter was flying in the vicinity of Bornholm Island, and it is expected to have been observing the Americans' activity.

US helicopters also took flights over other Nord Stream pipelines on September 10 and 19 and others stayed over the incident site for hours on the night of September 22 and September 25.

Reportedly, helicopters that made sorties on the night of September 22-23 and 25-26 have especially confusing tracks.

These revelations come after German newspaper Der Siegel reported Tuesday that the US Central Intelligence Agency (CIA) warned the German government there would be attacks on Nord Stream gas pipelines weeks ahead of any incident being reported around the pipelines.

An informed source told the German magazine that Berlin had been told by the CIA a few weeks ago that there would be attacks on the key pipelines supplying a huge portion of Europe's energy from Russia.