Gang wars are becoming an increasing concern in New Zealand, with some saying Australian deportees are to blame.

Criminals bringing their gang links to New Zealand is one of the key topics at the Police Association annual conference this week.

Assistant Commissioner of Serious and Organised Crime Richard Chambers told Mike Hosking it's a growing challenge.

He says gangs are expanding, the type of crime they're committing is more violent.

"It's all about influence. It's about using brand, the overt display of wealth and social media in an attempt to recruit."

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