The Bay of Plenty-based Mongols MC has been targeted in a series of police raids, with nine people facing a total of 228 charges.
Police said today that all of the gang's senior leaders and "the majority of patched members" have been arrested as part of the operation, which was carried out today.
More than 110 police staff were involved, including officers specialising on organised crime, and a total of 10 search warrants were carried out at properties across the Bay of Plenty.
Among the items found were a homemade bomb, cash, cannabis, methamphetamine, cocaine, ammunition, Molotov cocktails and eight firearms, including two AK-47s and two military-style semi-automatics.
A total of 19 vehicles were also seized today - five motorcycles, a light truck, a heavy truck, seven cars, four utes and a quad bike.
Detective Superintendent Greg Williams of police's National Organised Crime Group said the Mongols were part of the Australian Bandidos gang before being deported to New Zealand.
"During the course of this lengthy investigation, NOCG has been able to support a Bay of Plenty response to combat and prevent violent incidents stemming from this organised crime group," Mr Williams said.
"These have been as recent as 12 June and again on 15 June, where senior members are now before the court on serious charges, and a number of firearms and explosive devices have been seized.
"This proactive action was taken to prevent an attack on a rival gang.
"What this investigation will allege is that this organised crime group was involved in the sale and supply of methamphetamine and cocaine on a commercial level into the Bay of Plenty as well as across the North Island, causing significant harm to our communities.
"The ongoing violence between this organised crime group and other local gangs is simply about controlling a share of this drug market, and all these gangs have made it clear that they are prepared to use violence to protect their share.
"This includes not only arming up, but a very clear propensity to use these firearms and commit other violent acts such as arson, serious assaults, aggravated robberies and serious violence, seriously impacting on the wellbeing of Bay of Plenty communities at large."
Police said there have been six known shooting incidents in the Bay of Plenty involving the Mongols and other gangs.