Two naval helicopters collided in mid-air during a rehearsal session at the Royal Malaysian Navy stadium in Lumut, Perak, this morning.

According to the navy, all 10 people on board the two aircraft - three in a HOM (M503-3) helicopter, and seven in a Fennec (M502-6) chopper - were killed in the incident during a flyover training for the 90th Naval Day celebration, at 9.32am.

"The navy will set up an inquiry board to establish the cause of the incident.

"The navy urges the public to not circulate videos of the incident, for the sake of the (deceased's) families' sensitivities, and the investigation process," it said in a statement.

Horrifying footage of the two helicopters colliding in mid-air, before plunging to the ground, is making its rounds on social media.

Following the crash, the HOM (M503-3) helicopter plunged onto the staircase of the navy stadium, while the other chopper ended up near the navy sports complex's swimming pool.

Both aircraft had taken off from the Sitiawan field at 9.03am, before the tragedy occurred.