Seven US Marines and four soldiers are missing after an army helicopter crashed during a night training exercise in Florida.

The crash happened at Eglin Air Force Base in the Florida Panhandle.

Base officials say the Marines are part of a Camp Lejeune-based special operations group and the soldiers are from a Louisiana-based National Guard unit.

Military spokesman Andy Bourland said the CH-60 helicopter was reported missing at around 8:30pm on Tuesday local time.

Search and rescue crews found debris from the crash at around 2am on Wednesday.

"At this time all are missing," Mr Bourland said.

The helicopter went down during a routine training mission on a beach between Pensacola and Destin.

The beach is owned by the military and used for test missions.

Officials said the helicopter had taken off from a nearby airport in Destin and joined other aircraft in the exercise.