Sweden and Denmark summoned Russia's ambassadors Monday in protest over a near miss between a Russian surveillance plane and a commercial aircraft, a further sign of rising military tensions in the Baltic.

The incident took place Friday south of the Swedish city of Malmoe, shortly after the passenger plane -- operated on behalf of SAS -- departed from Copenhagen International Airport bound for Poland, the Swedish defence forces said.

Sweden -- which unlike Denmark is not a NATO member -- said the Russian plane came dangerously close to the SAS jet at less than nine kilometres (six miles), and that it was flying without an electronic transponder, making it invisible to commercial jets.

Both Swedish and Danish jet fighters were scrambled in response to the incident which reportedly took place in international airspace covered by Swedish air traffic control.

"It is totally unreasonable that civilian lives are put at risk in this way," Danish Foreign Minister Martin Lidegaard told news agency Ritzau, calling the incident a "rather serious situation".

"I hope that we can reach an agreement with the Russians in trying to limit these kind of flights."

Foreign Minister Margot Wallstroem said the Nordic countries' joint protest would be "very clear".

"The important thing here is that we believe that this is very inappropriate," she told reporters on the margins of an EU foreign minister's meeting in Brussels.

"We speak with one voice... Already yesterday (Sunday) we took contact with the Russian embassy and the meeting will take place today."

The incident happened amid growing concern in the Baltic region over signs of more assertive Russian behaviour, including Russian planes regularly skirting or violating the national air space of neighbouring countries.

Russia's annexation of Crimea and its involvmement in the conflict in eastern Ukraine has led to speculation that the Kremlin may be testing the mettle of Baltic Sea countries with an uptick in airforce activity.

A Russian military spokesman denied Sunday that there had been a near miss.

"No prerequisites existed for an air accident related with a flight of a Russian warplane in the international air space over the Baltic Sea," Russian Defence Ministry spokesman Igor Konashenkov told news agency ITAR-TASS.

He added that the plane was "more than 70 kilometres" (43 miles) away from the passenger jet and that a NATO reconnaissance plane was also in the area at the time.