Convicted murderer Nikki Roper suffered serious injuries today during an alleged assault at the country's most secure prison wing.

Roper, 26, was sentenced to life in prison for murdering his former girlfriend, Alexsis Maria Tovizi, in Christchurch in 2010.

A source said the attack at Auckland Prison at Paremoremo left Roper with a head injury and broken arm.

Department of Corrections northern regional commissioner Jeanette Burns said the inmate was being "treated at hospital and no update on his status is available".

"Corrections manages some of New Zealand's most difficult and challenging citizens, violence is always a risk as many offenders resort to violent behaviour as a means of resolving issues and of expressing themselves," she said.

"Prisoners can be volatile and unpredictable and many have long histories of antisocial behaviour. The department will not tolerate prisoners using violence against staff or other prisoners, and when this does occur the prisoner/s involved will be held to account for their actions."

The source said the attack on Roper was thought to be gang-related. He is currently being held in the prison's D-block, alongside New Zealand's most dangerous inmates.

After a High Court trial, Roper was found guilty of killing Ms Tovizi either by putting her in a sleeper hold or holding her head under water.

Roper then took her car and laptop, withdrew money from her bank account, and told family she had "done a runner".

He was convicted and sentenced at the High Court in Christchurch in 2013.

He appealed against his murder conviction on several grounds: that his trial lawyer made errors, the judge admitted prejudicial evidence and failed to explain certain points to the jurors, and that Roper was unfairly prevented from sitting next to his lawyer during the trial.

The Court of Appeal rejected each of the grounds as having no merit.