The Royal Commission of Inquiry into the Christchurch terror attacks will keep secret the submissions of several state agencies, including spy agencies, because of risks to public safety and national security.

The inquiry, chaired by Sir William Young, released a monthly update today and included the minutes of previous meetings that outlined what information was to be kept confidential.

It will keep secret all submissions from:

• the NZ Security Intelligence Service (NZSIS)

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• the Government Communications Security Bureau (GCSB)

• Police

• the Ministry of Business, Innovation and Employment

• Customs

• Department of the Prime Minister and Cabinet

• Ministry of Justice

• Ministry of Foreign Affairs and Trade

• The Inspector-General of Intelligence and Security

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It will also ban publication of the names of current or former employees of the NZSIS and the GCSB, as well as partner foreign intelligence agencies, or anyone connected to such people.

The heads of the agencies are exempted, and initial meetings have already taken place with NZSIS boss and Rebecca Kitteridge and GCSB boss Andrew Hampton.

The commission's terms of reference state that information must be kept confidential if its release would jeopardise a fair trial or endanger public safety, including for security or defence reasons.

That includes sensitive information received from other countries.

A blanket ban has been put in place because it is not practicable to separate material in advance that could be released without detrimental consequences.

The inquiry may have public hearings, where appropriate.

It is investigating the alleged gunman's activities before the attacks, including his travel in New Zealand and around the world, how he obtained firearms, his use of social media, and what relevant state sector agencies knew about him before the attacks.

It is also looking at what actions state agencies took, what more they could have down, and whether some of them, such as intelligence agencies, were too busy looking at Islamic fundamentalism at the expense of the threat of white nationalism.

The monthly update said the inquiry has offered to meet with affected families on their terms.

It also said that initial meetings had been held with the heads of several departments including Police Commissioner Mike Bush, as well as Christchurch Mayor Lianne Dalziel, Privacy Commissioner John Edwards, and Inspector-General of Intelligence and Security Cheryl Gwyn.

Work to form a Muslim Community Reference Group, which will help Muslim communities take part in the inquiry, was ongoing.

The commission is due to report back by December 10.