Following Friday's incident between a Russian military plane and a passenger jet off southern Sweden, NATO accused Moscow on Monday of endangering civil aviation in the Baltic region, Reuters reported.

Sweden claims a Russian military plane turned off its transponder (the tool that broadcasts the plane's location) and nearly collided with a Scandinavian Airlines passenger plane, but Russia maintains the planes were never less than 42 miles apart. Scandinavian Airlines also said that the incident has been blown out of proportion.

Speaking at a news conference on Monday, NATO Secretary General Jens Stoltenberg said, "It is not only a question of but it's the way they're conducting the flights. They are not filing their flight plans and they are not communicating with civilian air traffic control and they are not turning on their transponders."

"That poses a risk to civilian air traffic. The important thing is that NATO stays vigilant and that we intercept the Russian flights."

Sweden and Denmark both summoned their Russian ambassadors over complaints that lives were endangered in the incident, the Financial Times reported.

Denmark's foreign minister, Martin Lidegaard, said on Monday it was "totally unreasonable that civilian lives are put at risk in this way."

"I hope we can reach an agreement with the Russians that we try to limit these kinds of flights."

Peter Hultqvist, Sweden's defense minister, added that it was "serious, inappropriate and downright dangerous," for the Russian plane to fly with its transponder turned off.

While civilian flights are required to keep their transponders on at all times, military flights are allowed to turn them off when flying in international airspace, according to Reuters.

A similar incident in March saw a Russian plane without an active transponder flying within 300 feet of another Scandinavian plane.

NATO said it has scrambled fighter jets more than 400 times this year to intercept Russian military planes flying too close to foreign airspace in Europe.