Finland's Defense Ministry says it suspects a Russian military aircraft has violated Finnish airspace in the third such incident in six days.

Ministry spokesman Max Arhippainen told AP that a Russian AN-72 transport plane is believed to have crossed into Finnish airspace over the Gulf of Finland on Thursday.

He said the Border Guard is investigating the suspected infraction, which lasted a few minutes.

Arhippainen declined to say whether the Finnish air force intercepted the plane.

Finland reported similar incidents with Russian aircraft on Saturday and Monday. The Border Guard said the first was likely due to a maneuver to avoid a thunderstorm and the second is still being investigated.

Arhippainen said normally there are about four to six incidents a year of foreign aircraft entering Finnish airspace without permission.