Police seized a large cache of military-grade explosives at a private flat in the Konala district of Helsinki over the weekend. A number of both registered and unregistered weapons were also discovered.
Among the finds by police on Saturday were 1.5 kilos of gunpowder, several types of grenades and two mines containing the explosive TNT.
A loaded pistol, two rifles and ammunition were also seized.
Police had entered the flat in connection with another matter. The resident was taken into custody and investigations are continuing.