Malaysian navy officials announced that two of its helicopters collided in midair and crashed into the ground. All 10 crew members were confirmed dead at the scene.
The tragedy occurred at a naval base in the northern state of Perak on Tuesday morning.
Authorities say several choppers were flying in formation as a rehearsal for a parade celebrating the 90th anniversary of the Royal Malaysian Navy.
The navy has set up an investigation board to identify the cause of the accident.