Who is actually obstructing airplanes’ GPS in the Baltic?

.ON APRIL 29TH Finnair, Finland’s nationwide airline company, mentioned that it will suspend flights to the far eastern Estonian area of Tartu for a month. Last week pair of aircrafts were obliged to turn around after their GPS indicators were disrupted. General practitioner jamming has enhanced greatly in the Baltic region over the past pair of years.

Who is behind it and also exactly how dangerous could it be actually?