The Thames Coromandel mayor has come out swinging at a group of unruly teens who ran rampant in Whangamatā last night, rioting and causing carnage in the streets.

Twenty two people were arrested across Whangamatā as a result of the incident and other "hot spots" of disorder in the Coromandel town.

Mayor Sandra Goudie said they were nothing but "self-indulgent brats" who had been drinking at home and emerged to cause trouble later when they were "bored".

And it has emerged that close to $6000 worth of stock was stolen from a local cafe, and the Herald understands there are fears the roof is so badly damaged it will have to be replaced.

Last night a number of teens mounted the roof of Blackies Cafe, throwing bottles at police who armed themselves with shields and batons.

Eastern Waikato Area Commander Inspector Dean Anderson said groups in Whangamatā, particularly the Williamson Park area, were initially peaceful last night but there were "pockets of alcohol-fuelled violent disorder".

"After a number of people were injured from alcohol bottles being thrown into the assembled crowds, police commenced disbursing the main body of youths who had congregated around a local business within the park," Anderson said.

"A large number of youths had climbed onto the roof of the building and commenced throwing additional projectiles into the crowds and at police officers. The youths were eventually disbursed from the park area leaving significant damage to the business," he said.

Auckland woman Jane Phare, who is on holiday in the area, said there were thousands of teens gathered on the streets.

Some had climbed onto the roof of the cafe, next to the Whangamatā Surf Club, which is about 200m from her friend's bach where she was staying.

"There was just this roar of out-of-control drunk kids and no music," Phare said.

"There was a huge crowd of drunk teens who had climbed up on the roof. They were throwing bottles at police - there were bottles flying everywhere, smashing onto the ground.

"The road littered with broken glass and police were trying to keep young ones arriving away from bottles crashing down. Police were telling us to stay back.

"Riot police with shields and batons arrived at the club and everybody scattered."

Goudie spoke to Newstalk ZB about the incident this morning.

"That's been a real disappointment, because it's been so good for so long," she said of New Year in the area.

"Firstly, I've got to take my hat off to police for the awesome work that they do - they're our go-to guys.

"This riot has cost not only the property owners a lot of money, but it also costs the ratepayers a lot of money as well and so I'm really disappointed in seeing this start to rear its head again."

Goudie said years ago she can recall the area being "just like a warzone" with drunk teenagers after a "clampdown" stopping underage people from drinking in the streets and in public places.

"They got completely out of hand ... I hate to think what it was like last night when we've got record numbers on the peninsula," she said.

"Whangamatā has probably the biggest number of people in there it's seen for years ... it would have just been horrendous to be part of that or involved in that.

"It's just bored, drunk teenagers - they can't drink on the streets like they used to or in public like they used to so they do drink at home and then they bring themselves out onto the street and they're just self-indulgent brats."

Goudie said it is was possible an event for teenagers in future may prevent similar behaviour.

"That is a good way to go, I think, because it does give them something to focus on so they can put their energy into dancing and just cruising around with their peers and not cause damage that they have done in this instance," she said.

"However, this is at odds with some of the locals where they don't want those sorts of activities there.

"It's a bit of a judgment call and part of that judgement was that they didn't want to have anything on New Year's Eve to incite any sort of violent or aggressive behaviour from these young people, which includes these free concerts or any sort of concert.

"Either way, it seems to be fraught with difficulties."

A local businessman in Whangamatā is blaming last night's chaos, on a lack of events for young people.

Denis Beaver used to own Blackies cafe and says the council took away the ability for events a few years ago.

He says that's why last night's incident came about.