Prison officers in Northern Ireland watched - but did not intervene - as a mentally ill prisoner blinded himself in his cell.

Sean Lynch self-harmed on 20 occasions at Maghaberry Prison in Co Antrim on 5 June, 2014 - in an ordeal which lasted over an hour.

Four wardens watched for more than 15 minutes as Mr Lynch attacked himself, claiming they did not realise the seriousness of his injuries, according to a damning report by Northern Ireland's Prisoner Ombudsman Tom McGonigle.

They were also worried there could be a security risk if they intervened and he got hold of the prison keys.

"It seems remarkable that the officers felt it was neither necessary nor appropriate to enter his cell to prevent him from self-harming further," said Mr McGonigle.

"Their duty of care was trumped by security concerns that appear to have had little basis in reality.

"Although they complied with a strict interpretation of governor's orders which require intervention if a situation is life-threatening, Mr Lynch did not meet the definition."

The Ombudsman found his behaviour in prison had become "increasingly bizarre and violent".

Such episodes were dealt with by "short-term responses which included several moves of location and placements in observation cells with anti-ligature clothing".

Mr Lynch had faked symptoms on occasion, which led prison staff to believe he was trying to manipulate them into moving him to a different location.

But Mr McGonigle said: "This belief, which was partly caused by insufficient awareness of his mental illness, impacted negatively upon his management and care."

The head of Northern Ireland's prison service said she had never seen such an extreme case of self-harming in her 30-year career.

Director general Sue McAllister said the review showed "the difficulty of managing someone with severe mental health issues in a prison", adding it was important lessons were learned from the findings of the review.

Although medics had ordered a formal psychiatric assessment of Mr Lynch, he was treated as a routine referral from court.

He was supposed to receive six mental health reviews but only one took place and it took two weeks for him to see a psychiatrist.

A spokeswoman the South Eastern Health and Social Care Trust, which is responsible for healthcare in prisons, said: "The review highlighted that dealing with drug misuse and associated mental health issues within a custodial setting is very difficult.

"This has been a tragic outcome for Mr Lynch and we have already expressed our sympathy to him and his family.

"We will continue to work closely with Northern Ireland Prison Service to improve support for vulnerable people within the prison setting."