A 14-year-old is facing 81 charges following a string of serious incidents in Christchurch in recent weeks.
The teen faced charges of assaults with intent to injure, unlawful taking of a motor vehicle, aggravated robbery and theft.
Four youths were arrested between Thursday and Saturday last week in relation to a recent spate of vehicle thefts and assaults.
The other three arrested have been referred to Youth Aid.
Christchurch Metro Area Commander Lane Todd said he was confident the four were responsible.
"We're pleased to have quickly and comprehensively tackled what has been a significant run of offending by a small group of young people," he said.
"However it's hard to see these apprehensions as anything more than an inevitable end to a story that started long before any offence was committed.
"It's very rare that youth offenders come 'out of the blue'. We encourage communities to reach out to police if they're seeing concerning behaviour amongst their young people."
Tackling youth crime takes a multi-agency approach, with prevention at the heart of any solution, along with alternative resolutions for offenders in an effort to break a cycle of offending, he said.