Australia and close ally New Zealand have been monitoring three Chinese navy vessels -- a frigate, a cruiser and a supply tanker -- since they were spotted in international waters off the country's coast last week.

The Chinese ships issued a verbal live-fire warning by radio broadcast without prior notice on Friday that was picked up by commercial planes flying over the Tasman Sea between Australia and New Zealand, Canberra said.

The drill appears to be over, according to Australia's Department of Defence, which said "no weapon firings were heard or seen" from the Chinese task force despite it temporarily deploying a floating firing target.

"I don't think we have a satisfactory answer from China in relation to this," Defence Minister Richard Marles said.

"What happened yesterday was that the notice that was provided was very short," he told national broadcaster ABC.

Flights that had already taken off were "in a situation of needing to divert their course around the task group, and that was obviously disconcerting".

China had abided by international law but did not follow best practice of giving 12-24 hours' notice, and Canberra had raised the lack of notice with Beijing, Marles said.

Foreign Minister Penny Wong had also discussed it directly with her Chinese counterpart Wang Yi on the sidelines of a G20 meeting in Johannesburg.

New Zealand was working with Australia to monitor the task force and it, too, had no confirmation live firing actually occurred, said the country's defence minister, Judith Collins.

Beijing has described the manoeuvres as training exercises that were "safe, standard and professional" and in line with international law, without commenting on whether live ammunition was used.

- Tense encounters -

It was the latest in a string of tense encounters between China and Australia in the increasingly contested airspace and shipping lanes of the Asia-Pacific region.

Last week, Canberra rebuked Beijing for "unsafe" military conduct, accusing a Chinese fighter jet of dropping flares near an Australian air force plane patrolling the South China Sea.

A Chinese fighter jet was accused of intercepting an Australian Seahawk helicopter in international airspace in 2024, dropping flares across its flight path.

In 2023, a Chinese destroyer was accused of bombarding submerged Australian navy divers with sonar pulses in waters off Japan, causing minor injuries.

The Australian government says it respects the right of all states to pass through international waters and airspace.

The United States and its allies including Australia frequently cross through the 180-kilometre (112-mile) Taiwan Strait to reinforce its status as an international waterway, angering China, which claims jurisdiction over the waters.