All six people on board two helicopters were killed when the aircraft collided in mid-air and crashed onto the car park of a car dealership in the Brazilian coastal city of Rio de Janeiro, the news portal G1 reported on Sunday.
One of the helicopters exploded on impact and several cars caught fire.
One helicopter was carrying four passengers and a pilot, while the other had only the pilot on board.
The cause of the accident was initially unclear.
The air force, which is responsible for investigating aviation accidents, has launched an inquiry.
