Three people were hit in the face with full cans of alcohol during a riot at a Gisborne campground last night, St John Ambulance says.
The police, who arrested 63 people, say they themselves were pelted with cans and bits of wood.
Cars were overturned and tents were also set on fire at the campground for the BW Summer Festival music festival, which runs alongside the Rhythm and Vines festival.
The riot started about 5.30pm and St John district manager Shane Clapperton said five staff saw 83 patients in about two-and-a-half hours.
That included three people hit in the face with full cans of alcohol, who had been to be taken to hospital.
About 8000 young people attend the annual music festival, which runs separately to the Rhythm and Vines festival. However buses shuttle people between the two sites.
A police spokesperson said the rioting began when two groups from neighbouring campgrounds confronted each other over a fence. The fence was pushed over and the groups began fighting.
Up to 50 police officers were bought in to quell the unrest, with 10 ambulance staff and firefighters assisting.
The riot was well-planned and co-ordinated by a core group of festival goers who were intent on causing trouble, and it ws lucky no one was killed, the spokesperson said.
Alcohol was a major factor, and those involved were extremely intoxicated, Mr Clapperton told Summer Report.
"I do think alcohol is a major problem there. There is large consumption of alcohol by some individuals and, unfortunately, St John sometimes needs to look after those people who have over-indulged, both with alcohol and drugs.
"(It) ruins their day and means we have to spend our time looking after them."
Most of those treated at the scene suffered relatively minor injuries. Those arrested face charges ranging from disorderly behaviour to assault.
Gisborne Mayor Meng Foon said the riot was disappointing.
"For the last 10-11 years, they've been pretty well behaved," he said.
"It's never a good look when something happens like this but we're still optimistic."
Mr Foon said he could not explain why the council's licensing committee ignored police advice for controlled sales of alcohol.
"I've actually sent a note to the chairperson of the local liquor licensing committee and said to her they'd better heed to police advice next time," he said.
All good at Rhythm and Vines
Meanwhile, Rhythm Group chief executive Kieran Spillane said the Rhythm and Vines festival could not have gone any better.
About 18,500 people attended the music festival at Waiohika Estate, which is in its 12th year.
"We are delighted with the turn out for this years festival," he said.
"With the sun shining on Gisborne this holiday season, a strong international line up of artists, and a 18,500 strong crowd, our new year party could not be going any better.
"The Arcadia Afterburner all the way from Glastonbury is turning out to be a crowd favourite and it really has to be experienced to be believed."
Cathedral Square celebration
Further south, thousands of people packed Christchurch's Cathedral Square for the first concert there since the 2011 earthquakes.
Rock band Shihad headlined the show.
Those attending say it was fantastic to have such concerts back in the city.
Police said crowds in Dunedin, Queenstown and Wanaka were well behaved, with only a few minor incidents, and it was pleasing to see most people enjoying themselves responsibly.
Inspector Kelvin Lloyd said the vast majority of people had taken on board the police's prevention messages.
A Wellington police spokesperson said the capital's wet weather may have deterred revellers.
However, the skies cleared right on cue for about 2000 revellers who brought in the New Year in the Taranaki beach township of Oakura.
Reggae heavyweights the Black Seeds and Katchafire played under the big top at the venue about 12km south-west of New Plymouth.
Senior Sergeant John Fagan said most people behaved themselves in the Far North and enjoyed the Northland hospitality.
The busiest spot was Paihia, where a large fireworks display was put on, he said.
Bay of Plenty police also reported a relatively quiet night, with a low number of arrests at the traditional hot spot of Mt Maunganui.
Senior Sergeant Chris Foote said police were busy with big crowds in Auckland to watch the fireworks display.
But, like Wellington, rain dampened things down and it was business as usual aside from some arrests for alcohol-related offending and fights.
Think before driving
Assistant Commissioner Dave Cliff hoped that would carry through to today, and urged people to make sure they were fully sober before getting behind the wheel.
Under a new law that took effect on 1 December, the allowable blood-alcohol limit has been nearly halved from 80 milligrams down per millilitre of blood to 50.
Many drivers heading out on the road after a night's drinking did not realise how long alcohol remained in the bloodstream despite a night's sleep.
"The more you've drunk the night before, the longer it's going to take for your body to process all that alcohol.
"You'll still probably still be over the drink drive limit, unless you've had a very significant period between your last drink and the time you're thinking about driving," Mr Cliff said.