HELSINKI (AP) — Two Russian military aircraft are suspected of having violated Finland’s airspace close to its capital city of Helsinki, Finland’s defense ministry said Tuesday.

The ministry said in a brief statement that two Russian Su-27 fighter jets allegedly violated Finland’s airspace over the Gulf of Finland, near Helsinki, at around 2 p.m. local time (1100 GMT), Tuesday afternoon.

The Finnish Border Guard is investigating the incident.

Defense Ministry spokeswoman Nina Hyrsky told the Finnish news agency STT that Finnish Air Force F-18 jets were scrambled to intercept the Russian aircraft.

She told STT that the violation is suspected to have lasted about two minutes, and that the planes crossed about half a kilometer (0.3 miles) into Finnish airspace. Finland is not a member of NATO.

The Su-27 is a combat aircraft widely used by the Russian military to fly from mainland Russia to the nation’s Baltic Sea exclave of Kaliningrad, sandwiched between Poland and Lithuania.

The route passes a narrow international air corridor over