New Zealand and Australian defence forces are watching on cautiously, following China's military drills in the Tasman Sea. 

The Chinese Task Group conducted live firing last night from three vessels in its second day of drills. 

Defence Minister Judith Collins says its intentions had been broadcast via its radio channels.

Former politics professor Stephen Hoadley says Collins has been careful not to aggravate China with her choice of words. 

"She's showing a good deal of constraint, because in the back of her mind - or in the front of her mind - is the fact that China is still New Zealand's number one trade partner."

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