The cost of the Christchurch mosque shootings has topped $6 million for the Canterbury District Health Board.

The attack by a gunman on the Al Noor Mosque on Deans Ave and Linwood Islamic Centre on March 15 this year killed 51 people and injured 49.

"Canterbury DHB's initial response to the March terrorist attack has been quantified at $6 million," said a CDHB financial report.

CDHB chief executive David Meates added: "This has been derived from our internal costing systems, and covers the direct costs that have been incurred by Canterbury DHB in the initial response post-attack through to the end of June."

The Ministry of Health has approved additional funding of $3m for the CDHB.

Meates said the remaining costs would be funded from a population-based funding formula - a technical tool used to help evenly distribute the bulk of the CDHB's funding according to the needs of the population.

Additional costs will be added to the CDHB's deficit.

Meates has called the response from the health sector "truly extraordinary".

The raw numbers show the extensive lengths to which Christchurch Hospital was pushed in the aftermath of the event.

In the first 24 hours, 31 surgeries were performed. Over the following days and weeks, surgeons would spent 174 hours in theatre, while patients spent 3132 hours in ICU, and a staggering 19,566 hours on surgical wards.

Of the 48 shooting victims who arrived at Christchurch Hospital ED who were able to be resuscitated, 47 survived.

"I never dreamed our city would be impacted by such events, but it happened and even now nearly three months on, it still feels surreal," he told the Herald in June.

"I'm incredibly proud of the health system response to the attacks, which has been nothing short of extraordinary. The first two patients arrived at 1.50pm with cuts from having escaped from the Al Noor mosque through a glass window.

"Just five minutes later we activated our major incident plan. Most cities around the world would've dealt with this event in multi-trauma units, perhaps across multiple cities – we treated these patients in the one Emergency Department of Christchurch Hospital.

"I feel incredibly proud and so lucky to be part of a Canterbury Health System that is made up of so many amazing and talented people - teams of well-coordinated professionals and support staff each playing their part."

A 28-year-old Australian national has denied 51 murder charges and 40 attempted murder charges - along with a charge laid under the Terrorism Suppression Act 2002 - and is scheduled to stand trial next May.

The financial report also revealed other costs for the CDHB, such as industrial action, which has cost $2 million so far and the flooding of the outpatients building, which has cost $1 million so far.

Meates said separate financial reporting was needed to consider the cost of the measles outbreak.

- Additional reporting: Star.kiwi