American style street gangs are surging in New Zealand prisons, and a gang expert says they are "back in vogue" among youth.

While most gangs are growing their numbers in prisons, with members and affiliates at record levels, LA style street gangs like the Killer Beez, Crips and Bloods are among the fastest growing according to an Official Information Act response to Newshub from Corrections.

These younger gang members are targeting prison officers with attacks that are more violent and unpredictable than ever.

Corrections chief custodial officer Neil Beales told Newshub: "They are younger, they are more prone to violence, they're willing to go further and do more than perhaps we'd seen before."

He said it's far more than just a right hook or a left jab. "We're talking more weaponised assaults or stamping on heads, or stamping on peoples' backs, more vicious, more pack attacks."