Australia's defense forces, joined by New Zealand, have been monitoring Chinese navy vessels since they were spotted last week.

Three passenger flights from Sydney to Christchurch and Queenstown were in the air on Friday when they were first warned by a Chinese warship of a live-fire exercise, Australian media reported. The flights diverted and no one was put in danger, Australian defence minister Richard Marles told Australian Broadcasting Corporation radio.

Airliners were over the Tasman Sea crossing between Australia and New Zealand when the Chinese navy warned they were flying over a secret live-fire exercise, Australian Defense Minister Richard Marles said on Friday.

By Kirsty Needham, Lucy Craymer and Lisa Barrington SYDNEY/WELLINGTON (Reuters) -Australia expressed concern to China on Friday over the short notice given by the Chinese navy that it would hold a live-fire exercise in international waters between Australia and New Zealand,

New Zealand's navy said it observed a Chinese vessel firing live rounds in international waters. Earlier, on Friday, Australia condemned China for conducting similar drills in the region.

Australia's defense forces, joined by New Zealand, have been monitoring Chinese navy vessels since they were spotted last week.

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

New Zealand said the Chinese navy conducted a live-fire exercise in international waters near the Pacific nation on Saturday, a day after it held a similar drill between Australia and New Zealand that forced airlines to divert flights.