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.

Military experts said the presence of a Chinese flotilla had reinforced the vulnerabilities of Australia’s “old and small” fleet of warships.

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.

Defence Minister Richard Marles said China must explain its failure to provide sufficient notice for the live-fire training exercise in the waters between Australia and New Zealand on Friday.

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