A prisoner is in hospital tonight after being attacked by a fellow prisoner in Auckland this morning, at a prison which holds "some of New Zealand's most dangerous people".
The alleged attacker was "immediately detained" and is in directed segregation, Auckland Prison director David Pattinson told 1 NEWS.
The victim is in hospital, but his injuries aren't life-threatening, Mr Pattinson says.
"Violence in prison is not tolerated and anyone who resorts to this behaviour will held to account, including facing criminal charges."
Police confirmed to 1 NEWS they're investigating the assault. Mr Pattinson says Corrections will also carry out a fully investigation and "will ensure all evidence, including CCTV footage, is provided to police".
More than three-quarters of the prison population have convictions for violence in their offending history, Mr Pattinson says, calling the prisoners "some of New Zealand's most dangerous people".
More than 90 per cent of the prisoners have been diagnosed with a mental health or substance abuse disorder, he adds.