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.

Chinese warships warned they planned live-fire exercises in international waters off Australia’s eastern coast, an unexpected escalation of tensions between the two countries that diverted commercial airlines flying across the Tasman Sea.

The Chinese naval exercises, in international waters off Australia’s eastern coast, while legal, have nonetheless sparked alarm in Australia and New Zealand.

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