Parliament has unanimously passed a motion expressing New Zealand's condolences to the families of victims of Malaysia Airlines flight MH17, and criticising those who have impeded investigations into the tragedy.

Moved by Prime Minister John Key, the motion was also to register New Zealand's dismay at the "constraints that have been imposed by armed separatist groups" impeding the international investigation into the crash.

Mr Key said New Zealand called on those groups to co-operate immediately and unreservedly with international authorities, and he urged Russia to use its influence with those groups to ensure the investigation and recovery operation proceeded appropriately and unimpeded.

The New Zealand Government had been shocked by the tragedy and Mr Key said all New Zealanders would want to join with him in expressing their sadness to the families of the New Zealanders who perished.

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New Zealand was also saddened by the "grievous" casualties borne by other nations, particularly the Netherlands, Malaysia, and Australia.

Mr Key said he had spoken to the leaders of those countries to pass on New Zealanders' condolences.

Labour Leader David Cunliffe, Green Co-Leader Metiria Turei, NZ First Leader Winston Peters and Maori Party Co-leader Te Ururoa Flavell also spoke in support of the motion.

The motion was quickly followed by another from Mr Key expressing New Zealand's concerns at the deteriorating situation in Gaza and the mounting casualties there and calling for both sides to end hostilities, return to the negotiating table and hammer out an enduring two state solution to the conflict.