The involvement of the Finnish Defence Forces in the raids has added to this speculation. Surveillance planes and helicopters enforced a no-fly-zone over the Turku Archipelago as 100 armed agents swarmed the island in small boats. Another 300 were spread between the 16 remaining properties.
All reportedly had to contend with surveillance cameras and motion-detector alarms, despite their remote locations.
Pavel Melnikov owned the 17 raided sites mostly through his Finnish-based company Airiston Helmi. But Airiston, despite having invested millions since 2007, has never reported a profit.
"There are no commercial grounds for acquiring the land, but the roads are strategically important and their military significance is considerable," member of Finland's parliament Tom Packalen wrote for the newspaper Uusi Soumi.
"If Airiston Helmi is a truly commercial company, it's run by really bad business people or it's money laundering, which led police to lead a massive operation on the site."
Melnikov was not among just two men arrested during the raids. One is a Russian, and the other an Estonian of Russian heritage. Neither has been named.
Seven people had been held for questioning.
Melnikov himself remains out of reach. He claims Russian, Latvian and Maltese citizenship.
Finnish police say they seized $5 million in cash. Computers and flash drives containing some 100 terabytes of data was also reportedly confiscated.
It's not the first time Finnish media has raised fears of a potential Russian "hybrid warfare" campaign through strategic land purchases. Finland, which borders Russia to the East and Norway to the west, relies heavily on its western ports and Baltic Sea shipping lanes. There are also two major oil refineries in the area.
In 2018, Russian special forces staged an unannounced mock invasion of Gogland Island, close to the Finnish Coast.
The island is owneed by Russia and the raid involved the airborne insertion of special forces troops which "attacked" a simulated facility before helicoptering out.
It was widely seen as a "signal" to warn against Finland's improving relations with the West.
