A Canadian helicopter allegedly breached Finnish airspace on Monday afternoon, according to Finland's Ministry of Defence.
The ministry says the copter took off from a frigate in the Baltic Sea and flew over waters south of Utö island, which is in Finnish territory.
Monday's incident is being investigated by Finland's Border Guard as a suspected territorial violation, the ministry said.
There was a recent Finnish airspace incursion by NATO aircraft - two Spanish Hornet F-18 fighter jets - at the beginning of August. That violation reportedly took place south of Upinniemi. The peninsula in Kirkkonummi, west of Helsinki, is the site of a navy base.