An ADF member was assaulted and a cache of weapons was stolen from a patrol boat, moored at HMAS Coonawarra.

The Department of Defence said the intruder overpowered a duty member on board the boat and then ’’accessed the vessel’s armoury and removed a number of weapons’’.

The person then "departed the vessel with the weapons’’.

Northern Territory police have locked down the base and are searching all exiting vehicles.

HMAS Coonawarra is a naval base in Darwin, about two kilometres from the city centre. It would be common practice for there to be small arms on board a patrol boat.

NT Major and Serious Crime Detectives are investigating the incident, along with Defence personnel and the Australian Federal Police.

Chief of Navy Vice Admiral Ray Griggs told Fairfax Radio that he had initiated a review of security "more broadly across the fleet" on Friday morning, in the wake of the incident. 

"It's certainly a breach of security and it’s a very concerning one for me," he said, noting an incident like this had not happened before on a ship. The navy chief said that the young sailor assaulted in the incident was shaken but OK. 

"He's being looked after," he said.

Vice Admiral Griggs was not able to say what kind of weapons had been stolen.