The Chinese navy's Fuchi-class replenishment vessel Weishanhu and Renhai-class cruiser Zunyi. (Supplied: Australian Defence Force)
In short:
Defence officials have confirmed they were not given any advance notice of China's live-fire exercises in the Tasman Sea.
They said Air Services Australia notified Defence at about 10:10am — meaning they only became aware of the exercises about 40 minutes after China's window opened at 9:30am.
What's next?
The Defence Force chief also said it was unclear whether a Chinese nuclear-powered submarine was in waters near Australia.
Military officials say China's navy did not give them any advance notice before starting "disruptive" live-fire exercises in the Tasman Sea last week, confirming they were only alerted to the drills by a Virgin Australia pilot.
Defence Chief Admiral David Johnston told Senate estimates that Air Services Australia were warned of the drills at around 10am on Friday, after commercial airlines picked up a radio broadcast from the Chinese naval task group.
The agency alerted Defence about 10 minutes later — at around 10:10am — meaning it was only aware of the exercises 40 minutes after China's navy opened a "window" for live-fire exercises from 9:30am.
How Australia learnt of the drill
Friday, 9:30am: The Chinese task group begins their live-firing drill.
9:58am: Virgin pilot notifies Airservices Australia.
10:00am: Airservices Australia alerts flights about the exercise.
About 10:10am: Airservices Australia notifies the Australian Defence Force.
In evidence to Senate estimates, Defence said New Zealand's navy also picked up the message and passed it on to the Australian Defence Force — but that alert did not reach them until around 11:00am.
Admiral Johnston said that delay was not surprising because communications channels from Air Services Australia were "more direct" than military procedures.
"[The] military reporting chain would have moved through the New Zealand reporting system and then into providing advice for Australia," he told the Senate committee.
"So they both heard [the warning] at the same time but the means of reporting them is always going to be more direct from an aircraft."
Coalition frontbencher James Paterson pressed senior Defence officers and officials on the timeline, saying China's navy had failed to provide even basic transparency.
Chief Admiral David Johnston appeared before a Senate committee on Wednesday. (ABC News: Ian Cutmore)
"It's not really a notification for an upcoming exercise if we only find out about it after it's commenced," he said.
Admiral Johnston said he agreed the notification was "inadequate" and reiterated that Australia would have preferred China's navy to give at least 24-48 hours' notice.
When pressed on whether the Chinese navy's behaviour could be described as "provocative", Admiral Johnston said he would describe it as "irresponsible" and "disruptive".
Defence told the committee that the Chinese warships had now moved back into Australia's Exclusive Economic Zone and were now about 250 kilometres south of Tasmania.
People's Liberation Army-Navy Jiangkai-class frigate Hengyang in the Tasman Sea. (Supplied: ADF)
The ABC reported this morning that Defence officials believe a Chinese nuclear-powered submarine could be accompanying the task force, for at least part of its deployment.
The Defence Force chief told the committee that it was not clear if a Chinese submarine was in waters near Australia.
"I don't know whether there is a submarine with them, it is possible, task groups occasionally do deploy with submarines but not always," he said.
"I can't be definitive whether that's the case."