An Auckland Prison staff member was seriously injured in an attack by an inmate on Saturday, the Department of Corrections says.
The assault happened shortly after 8pm on Saturday, when the staff noticed a damaged cell door.
The guards were inspecting the door when the male prisoner, who had escaped from his cell, attacked them from the corridor.
One of the staff was taken to hospital with serious injuries, while the other was seen by a nurse at the prison.
Additional staff responded and began negotiating with the man, who complied with instructions and was moved in handcuffs to another cell.
The prisoner was already being managed on a highly restricted regime of directed segregation for a persistent pattern of assaulting staff and non-compliant behaviour.
Corrections Regional Commissioner Lynette Cave said additional staff have been rostered on tonight and there will be increased patrols.
"The staff who responded to this situation initially, and those that came to the aid of their colleagues, did an exceptional and brave job. Corrections officers come to work every day to keep New Zealanders safe.
"They work in highly challenging circumstances with some of the most dangerous, difficult and unwell people in New Zealand. The assault on them last night was unprovoked and gutless," Cave said.
The assault has sparked two separate reviews, one by the Department of Corrections and the other by Cusman Wakefield which maintains the prison.