Defence forces have started counter-terrorism training across Sydney and the Hunter Valley.


Black Hawk helicopters, watercraft and special purpose military vehicles will be moving through some parts of Sydney during the training, which runs from today until Friday.


Weapons will be carried by those participating in the training but nothing will be loaded with live ammunition.


Most of the training will be done outside business hours and Defence says it will try to minimise disturbances to local residents.


AAP