As the excitement of the Rugby World Cup builds and New Zealand fills with visitors, the Independent's Sydney-based correspondent Kathy Marks files this story to the UK.
It is late afternoon in Wairoa, a country town in New Zealand's picturesque Hawke's Bay region. In the park, Lambton Square, several dozen teenagers are performing press-ups, warming up for their after-school rugby training.
The peaceful scene is a sharp contrast to three days earlier, when a rugby league match ended with members of a Maori gang, the Mongrel Mob, firing a sawn-off shotgun into the air. No one was hurt, but the incident - apparently provoked by the presence of a rival gang, Black Power, among the spectators - terrified the Saturday afternoon crowd of mainly families.
These events may seem out of place in a country whose marketing slogan is "100 per cent pure". New Zealand, though, has an entrenched gang culture, and rarely a week passes without trouble erupting. Wairoa - 90 minutes' drive north of Napier, an Art Deco city popular with tourists and one of the Rugby World Cup venues - is the latest flashpoint.
This is a side of New Zealand that World Cup fans - descending for the six-week competition which began on Friday in Auckland - are unlikely to see; indeed, most locals are never affected by it. But it reflects the uglier aspects of a nation widely perceived as clean, green and safe.
Gangs thrive in areas with big Maori and Pacific Islander populations and high levels of crime, poverty and unemployment. Maori, in particular, are at the bottom of the socio-economic heap in New Zealand. They are also largely responsible for its shocking rates of domestic violence and child abuse - the country's "dark secrets", as a former Governor-General, Dame Silvia Cartwright, called them.
The issues were highlighted in the 1994 movie Once Were Warriors, set in the bleak suburbs of South Auckland. Seventeen years on, violence continues to plague Maori communities. Some sociologists blame the Maori "warrior culture", which they claim is glorified by the gangs.
Gangs are active across New Zealand, even in small rural communities. Wairoa is a Mongrel Mob stronghold; Frasertown, five miles to the north, is Black Power territory. Both gangs - Maori-dominated and implacable foes - have savage reputations, with a history of murder, gang rape and ruthless "payback".
Lately, though, the gangs have been trying to clean up their image, with some leaders renouncing violence and preaching mainstream values. Rex Timu, president of the original Mongrel Mob chapter in Hastings, near Napier, instructs would-be recruits to "go away and get an education". Timu, who has the Mongrel emblem - a bulldog with a German helmet - tattooed on his bulky left forearm, also warns them: "Don't join us if you want to do an armed robbery or kill someone. That's not our way anymore."
The problem is, not everyone heeds the message. In Wairoa, an edgy town bisected by a broad river, people are sick of the gang wars. One spring evening last year, a man walked up to a truck in a petrol station and shot the driver, a Mongrel Mobster, through the window.
Of the Maori gangs, the Mob and Black Power are the biggest and most feared. They formed in the wake of post-war Maori mass migration to the cities. Radical reforms to the New Zealand economy in the 1980s created large-scale unemployment, with Maori worst affected.
With adults dislocated from their roots and culture, and battling alienation and discrimination, families collapsed. Absent fathers became commonplace, and an epidemic of alcoholism, drug abuse and domestic violence began. For young people, the all-male gangs were like substitute families. They were an escape route, offering status, protection, even a career - selling drugs. They were also places where violence flourished. The violence spilt back into homes. New Zealand women suffer the highest rate of domestic violence in the developed world; the country also has one of the Organisation for Economic Co-operation and Development's worst child murder rates. "[Gang members] use the iron fist instead of talking," observes Bruno Isaac, a former Mongrel Mob leader and author of a book about the gang, True Red.
I met Isaac, who has a full facial moko (traditional Maori tattoo), at the Saturday market in Otara, the Auckland suburb where Once Were Warriors was filmed. He was selling his book from the back of a motorbike. It is full of lurid tales of gang life.
"Women were there to cook our kai [food] and give us pleasure - they were simply chattels, meat we could consume and spit out," he writes. In order to obtain "the patch" - the right to display the gang emblem on clothes and in tattoos - recruits had to pass tests such as "drinking excrement and urine from a gumboot, raping someone, or fighting three guys at once".
In Hawke's Bay - known internationally for its wineries - some families are into their third generation of gang membership. Getting older, having children and serving time has mellowed some leaders. "We want to stop the criminality and look after our families, look after ourselves," declares Timu.
Timu, coolstore supervisor at an apple exporting company, served an eight-year sentence for gang rape in his youth. He blames the continuing violence on young men trying to prove themselves. "I used to be like that - I would go out and beat someone up for no reason." The Mob, he insists, flashing a gold tooth, is "like any other social club - we have a beer, talk about politics and rugby".
Mane Adams, president of the Napier chapter of Black Power, purveys an equally responsible message. He is chairman of his local marae (communal meeting place), and a campaigner against methamphetamine, or "crystal meth". Adams says: "I don't see myself as a gang leader, rather as a role model and mentor."
He and Timu enjoy a "rapport" that enables them to defuse trouble. They attend meetings with police, politicians, mayors. Yet neither man has quite abandoned the gang mentality. Adams says: "If they [the Mongrel Mob] play up, we have to respond to it, otherwise people will say we're going soft."
Both leaders operate their own rough justice. Adams recently had to "run over" a motorcycle gangster selling methamphetamine on his turf.
Incidents like the Wairoa shooting, meanwhile, set back their reforming efforts. They also inflame wider tensions.
In 2006, a New Zealand geneticist, Rod Lea, asserted Maori carry a "warrior gene" that predisposes them to violence. The claim was widely criticised. However, Greg Newbold, a Canterbury University criminologist, blames the glorification of the Maori "warrior ethos" embodied in the haka, or war dance, that the All Blacks rugby team perform before each match, for the family and gang violence.
"The culture of the warrior is very powerful in the Maori psyche, and the celebration of male domination and machismo is still very evident," Dr Newbold says.
Jim Anglem, of the Violence Research Centre, rejects this notion, saying women and children were revered in traditional Maori society. Moreover, between 1950 and 1970 there was little evidence of Maori family violence. That, along with the fact that middle-class Maori families are no more violent than their European counterparts, supports the theory that socio-economic factors are key.
Greg O'Connor, president of the New Zealand Police Association, is cynical about the efforts of those seeking to rebrand the gangs, calling them "pure PR". "If they've still got a patch on their back, they're bound to the ethos of the gang," he says.