A German frigate is suspected of violating Finnish territorial waters in Northern Ostrobothnia on 18 January, Ministry of Defence stated in a press release.
According to the ministry, the vessel was carrying out tests when the suspected brief violation occurred off the coast of the municipality of Raahe in western Finland.
Communications director at the Ministry of Defense Niina Hyrsky confirmed to Yle that the vessel was a frigate.
"The vessel travelled a few hundred metres into Finnish waters," Hyrsky said.
Hyrsky however said she is not in a position to disclose the type of test activity the frigate was conducting for another state's operational activities.
The Finnish Border Guard is currently investigating the incident. According to Hyrsky, the Finnish foreign ministry has asked the German Embassy in Helsinki for an account of the incident.
In July last year, Finland's Border Guard confirmed that a Russian aircraft entered Finnish airspace over the southern coastal city of Porvoo, which is about 50 km east of Finland's capital Helsinki.
In April 2019, Portugal's Air Force confirmed that one of its surveillance aircraft had "inadvertently entered Finland's airspace" above the Upinniemi peninsula in Kirkkonummi, on Finland's southern coast.