A Russian military jet nearly collided with a commercial passenger plane that had just taken off from an airport in Denmark, the Swedish military said Saturday.

The incident happened Friday south of the Swedish city of Malmoe, shortly after the passenger plane had departed from Copenhagen International Airport, the Swedish defence forces said.

"We have confirmed through the Swedish defence ministry that the aircraft was Russian," Johannes Hellqvist, a spokesman for the Swedish defence forces, told AFP.

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

Concerns are fuelled by the role Russian has been playing the Ukrainian crisis, including the annexation of Crimea.

Both Swedish and Danish jet fighters were scrambled in response to the incident Friday, Hellqvist said.

The Russian plane never actually violated Swedish air space, Sweden's Defence Minister Peter Hultqvist was quoted by Swedish news agency TT as saying.

Hultqvist said the Russian airplane had been flying without a transponder -- an electronic identification device that would have made it visible on the radar of the commercial plane.

He described it as "irresponsible" for Russian planes to frequently fly without transponders.

"There is a risk that accidents could occur that could ultimately lead to deaths," he said according to TT.

The passenger plane was not immediately identified. According to the website of Danish newspaper Politiken, it was on the way to Poland.

In March this year, an accident was even closer to happening, when a plane from Scandinavian Airlines came within 100 metres (330 feet) of a Russian aircraft.

Poland's defence minister, Tomasz Siemoniak, warned Thursday that in recent days there had been "unprecedented Russian activity from its Baltic fleet to flights over the Baltic Sea", and on Friday his coounterpart in Estonia said a Russian plane had violated its airspace.