Foreign Minister Penny Wong said she was worried about the lack of transparency surrounding the "live fire exercises", and would be raising her "concerns" with Beijing.

"We will be discussing this with the Chinese," she told national broadcaster ABC from Johannesburg, where she was attending a G20 meeting. 

The drills sparked a warning from Australia's air safety agency, forcing some commercial flights to alter their course. 

"As a precaution, we have advised airlines with flights planned in the area," government agency Airservices Australia said in a statement. 

"We are also working together to coordinate advice to operators and pilots." 

Airlines modified flight paths between Australia and New Zealand on Friday after China notified Australia that the People's Liberation Army Navy would hold live-fire exercises off the New South Wales coast.

Australia's Prime Minister Anthony Albanese told reporters on Friday afternoon that the time period for the Chinese navy exercises had expired, and it was unclear if live fire had been used by the Chinese navy.

"China issued, in accordance with practice, an alert that it would be conducting these activities, including the potential use of live fire. It's outside ofAustralia's exclusive economic zone," he said, indicating it was at least 200 nautical miles (370 km) offshore.

"According to defence, there has been no imminent risk of danger to any Australian assets or New Zealand assets, and that's why this notification occurs," he added.

A People's Liberation Army Navy frigate, cruiser and replenishment vessel last week entered Australia's maritime approaches, and travelled downAustralia's east coast this week, monitored by the navies and air forces of Australia and New Zealand.

Airlines were contacted by Australia's air traffic control agency on Friday warning them of reports of live fire where the Chinese navy task group was operating, the agency and Australian officials said.

"The Civil Aviation Authority and Airservices Australia are aware of reports of live firing in international waters," air traffic control agency AirservicesAustralia said in a statement.

"As a precaution, we have advised airlines with flights planned in the area," it added. 

Qantas and its low-cost arm Jetstar were monitoring the airspace and temporarily adjusted some flights across the Tasman Sea betweenAustralia and New Zealand.

Air New Zealand said it had modified flight paths as needed to avoid the area, with no impact to its operations, while Virgin Australia was following instructions from Airservices Australia.

Australia's defence department has been monitoring the Chinese navy vessels -- a frigate, a cruiser and a supply tanker -- since they were spotted in international waters last week. 

Although the ships are sailing in international waters, officials have described their presence as "unusual". 

The ships were reportedly within 150 nautical miles (about 280 kilometres) of Australia's mainland earlier this week.