A nurse at Christchurch's Hillmorton Hospital was strangled and dragged across the floor by a patient over the weekend, her colleagues say.
The alleged serious assault at the hospital's acute inpatient mental health unit is the latest in a string of such incidents, which staff are blaming on inadequate staffing and the lack of an intensive care unit.
Several nurses at the mental hospital have told RNZ a nurse was strangled and dragged across the floor by a psychotic patient over the weekend.
This comes just weeks after RNZ revealed that over the past 12 months, staff at the unit were assaulted up to 30 times a month.
A nurse, who did not want to be named, said it was getting too much.
"There were several assaults on nursing staff in acutes over the weekend... [That] one in particular was very nasty," they said.
"A female nurse was strangled, then dragged along the ground by a psychotic male patient... The situation was exacerbated by inadequate staffing.
"It's not good, morale is at rock bottom."
The nurse said part of problem was the building itself.
An intensive care unit, or ICU, would be a huge help, as - if properly staffed - it would allow nurses to more easily manage the most volatile patients, the nurse said.
The acute unit used to have an ICU, but it was scrapped in 2013 and replaced with a three-bed high care area in each of the four wards.
The nurse said these were not safe.
"These high care areas are isolated and dangerous for patients and staff alike," they said.
"Often inexperienced nurses are placed there to care for psychotic, aggressive and dangerous patients.
"Many of these young nurses are anxious and at times downright scared.
Another nurse who spoke to RNZ said the reason the areas were so dangerous was due to their design.
Some of the offices attached to each high care area only had one entrance, and it led directly into the area itself.
That meant there was no escape when things went wrong, the nurse said.
As an immediate fix, Nurses Organisation spokesman John Miller said the union had again asked Canterbury district health board to place security on the wards.
"We have raised this before and the DHB have given good reasons why they aren't keen, and are looking in the long term at employing another type of support worker in that environment," he said.
"But we want them to look at a short-term interim measure of getting some security on those wards."
He wanted that to happen as soon as possible.
A steering group, made up of nurses and management, was being set up to look at addressing issues at the unit, Mr Miller said.
It had its first meeting last week and Mr Miller was hopeful it would lead to change.
The DHB has not yet responded to requests for comment.