Immigration New Zealand says it is looking at ways to see how families of the Christchurch mosque shooting victims - many who are here on temporary visas - can be allowed to remain.

Some of the 50 people killed in the shootings at Masjid Al Noor and Linwood mosque are understood to be on temporary visas, and many are possibly principal applicants on visa holders.

Under immigration rules, their deaths would mean their families no longer met visa requirements.

"INZ acknowledges that there are a number of people who have been affected by the shootings in Christchurch on Friday," said Peter Elms, INZ assistant general manager.

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"We are currently working through possible options for those on temporary visas who have been affected."

Migrants from Malaysia, Bangladesh, Indonesia, Pakistan, Turkey, India, Jordan and Saudi Arabia are believed to be among those who have either been killed or injured by the attacks.

Many had come to New Zealand with dreams of one day getting residency for themselves and their families.

Canterbury District Health Board chief executive David Meates confirmed 34 attack victims were being treated, including 12 in intensive care in a critical condition.

"These are unprecedented circumstances for everyone and INZ is committed to ensuring we do all we can to support those who have been impacted," Elms added.

Zain Ali, University of Auckland professional teaching fellow and former head of Islamic Research said the Islamic Friday congregational prayer, or Jumu'a, is compulsory for post-puberty males.

"They would have been fathers, brothers...and it wouldn't surprise me if most of them are breadwinners for their families," Ali said.

They are also likely to be the families' principal visa holders or applicants.