Operation Burnham Inquiry chairman Sir Terence Arnold says much of the information relevant to the inquiry is likely to remain classified and not able to be disclosed.

Arnold made the comments in his opening of the first of three "modules", a series of public hearings on the inquiry. It is being held in central Wellington.

The inquiry had established a process for reviewing classified information which had led to some additional information being publicly disclosed. The review process was continuing and likely to result in the disclosure of more currently classified information, Arnold told the hearing.

"The inquiry does understand the public interest in its work and wishes to be as open as it can in the circumstances. In addition to meeting its obligations to core participants, the inquiry wants to do what it can to assist public understanding of the issues.

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The inquiry is named for the August 2010 NZ Special Air Service (SAS) operation in Taliban-held Afghanistan to target insurgent leaders behind attacks on New Zealand and other coalition troops.

The raid was disclosed in the 2017 book Hit & Run by Nicky Hager and Jon Stephenson which claimed the SAS had carried out a "revenge" raid which left six civilians dead, including a 3-year-old girl named Fatima. Another 15 were wounded, the authors claimed.

The assault came after the August 4 2010 death of New Zealand Lieutenant Tim O'Donnell in a province neighbouring the Bamiyan district where New Zealand's Provincial Reconstruction Team was based.

The New Zealand Defence Force (NZDF) has rejected the claims, saying nine insurgents were killed.

The Government announced in April last year that an inquiry into Operation Burnham and related matters would be held.

The inquiry aims to establish the facts in connection with the allegations, examine the treatment by the NZDF of the reports of civilian casualties and look at the conduct of NZDF personnel forces.

It is being led by former prime minister Sir Geoffrey Palmer and Arnold, a former Supreme Court judge.

Human rights lawyer Deborah Manning, who represents Afghani villagers in the inquiry, has launched legal action seeking a judicial review of the investigation which she says should be more open. That matter will be heard later this month.

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Former Australian Defence Force Chief Air Chief Marshal Sir Angus Houston will present to the hearing today.

He will describe the nature of the conflict from a military perspective, give an overview of military structure and decision-making processes and describe the role of special forces generally.

Wayne Mapp, who was the New Zealand defence minister at the time, will then discuss the Government's decision in 2009 to deploy the SAS and how decisions were made about specific operations at the time.

Arnold said today's hearing would be a scene-setting exercise.

"Apart from the question of the location, which I will come to shortly, the presentations largely deal with matters that are, from the inquiry's perspective, givens."

Arnold said the inquiry was not concerned with whether or not the SAS should have been to deployed to Afghanistan in 2009 but with allegations about its conduct during that deployment.

The hearing continues.