China's naval exercise in the Tasman Sea has put Australia and New Zealand on alert, with Canberra calling it "unusual".

China issued a warning Friday of potential "live fire" naval drills in international waters off Australia's eastern coast but gave little prior notice, disrupting commercial air flights, the Australian government said.

Airlines have been contacted by Australia’s air traffic control agency warning them of reports of live fire off the country’s east coast where a Chinese navy task group has been operating, the agency and Australian officials said.