An Auckland inmate has died after being attacked by a fellow prisoner inside Paremoremo Prison.

The attack took place in a prison yard shortly before 3pm today, Corrections chief custodial officer Neil Beales confirmed.

"The alleged assault occurred in the unit's yard. Staff responded to stop the assault and provide medical assistance to the victim," he said.

The alleged attacker was now in segregation in the prison management unit.

Corrections will carry out a full investigation, and ensure all evidence, including CCTV footage, is provided to police, Beale said.

Police confirmed the incident was also reported to them this afternoon

"One person sustained serious injuries and despite being provided medical assistance, they have died at the scene," a police spokesman said.

Police were making inquiries to establish the circumstances of the death.

"At this early stage police are not in a position to comment further," the spokesman said.

St John were called to the prison at 2.40pm, a service spokeswoman said.

"We deployed one manager and two ambulances," she said.