Navy helicopter crashes off coast south of Sydney, injuring nine

A Navy helicopter has crashed off Jervis Bay, about 150 kilometres south of Sydney.

ACT Police and rescue helicopters were helping the Defence Force respond to the incident about 9.10pm on Wednesday.

Paramedics said nine people escaped the aircraft with very minor injuries.

"It's just crashed," one bystander can be heard saying in video taken at the scene, which is near the HMAS Creswell training base.

It's unclear what caused the crash.

Authorities said they were still seeking to confirm details.

More to come.