Planes flying between Australia and New Zealand have been diverted as China conducts a closely-scrutinised military exercise in nearby waters that may involve live fire.

The rare presence of three Chinese naval ships in the Tasman Sea has put both antipodean countries on alert in recent days, with Australia calling it "unusual".

Australian airline Qantas told the BBC it "temporarily adjusted" the routes of its planes and other carriers have reportedly done the same.

China has said the exercise, which is taking place in international waters, is in accordance with international law.

The ships are now reportedly 340 nautical miles east of the New South Wales coast of Australia, although they were said to have come as close as 150 nautical miles from Sydney at one point.

Australia and New Zealand have been closely monitoring the Chinese fleet - a frigate, a cruiser and a supply tanker - since last week, and have dispatched their own ships to observe them.

Earlier this week, New Zealand's Defence Minister Judith Collins said China had not informed them they would be sending warships to their region and "have not deigned to advise us on what they are doing in the Tasman Sea", according to the New Zealand Herald.

Meanwhile, Australia's Defence Minister Richard Marles said that the ships' presence was "not unprecedented, but it is an unusual event".

China's foreign ministry confirmed on Friday they were doing naval training and exercises in "distant waters".

"The exercises were conducted in a safe, standard, and professional manner at all times, in accordance with relevant international laws and practices," spokesman Guo Jiakun said.

Australia's Prime Minister Anthony Albanese said the Chinese fleet issued an alert on Friday that they would start conducting exercises which may involve live fire.

"This is activity that has occurred in waters consistent with international law... there has been no imminent risk of danger to any Australian assets or New Zealand assets," he said.

But Marles said the Chinese had not directly notified Australian officials when they put out the alert.

"What China did was put out a notification that it was intending to engage in live fire, and by that I mean a broadcast that was picked up by airlines, literally commercial planes that were flying across the Tasman," he told the Australian Broadcasting Corporation, adding that usually such notices would be given 12 to 24 hours in advance.

On Friday an Emirates plane was reportedly informed about the exercise by Chinese authorities, while it was still in the air as it flew from Sydney to Christchurch. The BBC is seeking confirmation.

In a statement to the BBC, Qantas confirmed that it had changed the routes of its planes flying across the Tasman Sea and said it was continually monitoring airspace.

"We continue to work with the Australian government and broader industry to monitor the situation," it added.

Virgin Australia and Air New Zealand have reportedly done the same.

The drill comes just days after Australia and China held a defence dialogue in Beijing where they had discussed military transparency and communication, among other things.

The two countries have seen several recent tense maritime encounters.

Earlier this month, Canberra said a Chinese fighter jet had released flares in front of an Australian military aircraft while flying over the South China Sea. Beijing said the aircraft had "intentionally intruded" into its airspace.

In May last year, Australia accused a Chinese fighter plane of dropping flares close to an Australian navy helicopter that was part of a UN Security Council mission on the Yellow Sea.

Canberra accused Beijing's navy of using sonar pulses in international waters off Japan in November 2023, resulting in Australian divers suffering injuries.