Two Russian fighter jets entered Finnish airspace near Porvoo in southern Finland at the end of July, according to a report by the Finnish Border Guard.
According to an investigation, the SU-27 jets invaded Finnish airspace at 2:07 pm on 28 July. The violation lasted about one minute, during which the aircraft covered a distance of 10 kilometres. The aircraft entered about 600 metres into Finnish airspace, according to the agency.
The investigation into the incident was conducted by the Border Guard's anti-crime unit of the Gulf of Finland Coast Guard.
Because the identity of the pilots was not known it is not possible to press charges over the incident, the Border Guard said.
Edited at 17:28 to clarify that the aircraft entered about 600 metres into Finnish territory - not flying at an altitude of 600 metres.