Finland announced Friday that it is suspecting that a Russian vessel violated territorial waters in the eastern Gulf of Finland.
Investigations are being conducted after the suspected territorial violation took place on Friday afternoon, the Finnish Defense Ministry said in a statement.
"The Border Guard is investigating the incident and will provide further information as the investigation progresses," the ministry said.
The Nordic country last month said four Russian military planes had violated its airspace on June 10.
The incident comes as relations between Helsinki and Moscow have become increasingly tense after Finland followed by Sweden joined NATO last year.
The Nordic country's NATO membership drew military threats from Kremlin with Russian President Vladimir Putin accusing the west of "dragging" Finland into military alliance and creating rift between Moscow and Helsinki.
In December, Finland, which shares a 1,340-kilometre (830-mile) border with Russia, closed entry with the Finnish authorities accusing Moscow of carrying out a suspected "hybrid attack" and purposefully assisting undocumented migrants in crossing into the Nordic country, which Russia denied.
