Some 49 flights were forced to divert last week when three Chinese warships announced live firing drills underneath a busy flight path halfway between Australia and New Zealand.

Both nations have criticised China for staging the drills with little notice -- Australian officials said the last-minute alert was broadcast on a channel unused by air controllers.

"In my view, the notice is appropriate," ambassador Xiao Qian told national broadcaster ABC.

"I don't see there's any reason why the Chinese side should feel sorry about that, or even to think about apologising for that."

Australia and close ally New Zealand have been monitoring the vessels -- a frigate, a cruiser and a supply tanker -- since they were detected in international waters off Australia last week.

Officials said 49 commercial flights were forced to divert around the live firing zone on February 21.

Australia said the drills took place in international waters, and has conceded China's conduct abided by international law.

"As a major power in this region... it is normal for China to send vessels to different parts of the region to conduct various types of activities," Xiao said on Friday.

The warships were moving through an oceanic expanse off Australia's south coast on Friday morning known as the "Great Australian Bight", New Zealand's defence force said.

It added it was ready to "support Australia by providing military assets for further monitoring should the need arise".