Censor.NET reports citing Associated Press via Irish Independent.
The accident took place near the village of Cerveny Kamen, according to Zuzana Farkasova, a spokeswoman for Slovakian firefighters.
Juraj Denes, an official with the Slovak government agency that investigates plane crashes, said preliminary information suggests 40 people were on board two Let L-410 planes at the time of the collision, which occurred at about 5,000ft.
Denes said parachutists in one of the planes survived because they managed to jump out before the collision.
Andrej Hirjak, a spokesman for the rescuers, said three helicopters were being used by rescue workers to reach the crash site in a hilly area near the border with the Czech Republic.