North Island hospitals are receiving Christchurch earthquake victims and plan to send specialists to help in the devastated city.

Civil Defence Minister John Carter said possibly hundreds of people had been injured during the earthquake.

Auckland District Health Board said last night arrangements were being made for two injured patients to be flown to Auckland - a woman, to be treated at Auckland City Hospital, and a child bound for Starship.

Six triage centres have been set up in Christchurch - two at hospitals, and one each at an accident and medical centre, a park, a factory and a mall - to assess and cope with the injured.

Canterbury DHB chief executive David Meates said Christchurch Hospital had received large numbers of patients after the earthquake, many with serious injuries.

People with injuries that were not life-threatening were being assessed and treated at the outpatients department and at Christchurch Women's Hospital. The hospital was expecting a second wave of casualties to arrive last night - people who had been rescued by urban search and rescue teams.

Mr Meates said Christchurch Hospital and other hospitals in the region had been damaged.

Up to 50 stable medical patients were to be transferred last night from Christchurch Hospital's Riverside Block, to two other public hospitals in the city and the private South Cross Hospital, to make way for people injured seriously in the earthquake.

Elective surgery and outpatients' appointments have been postponed until tomorrow at Christchurch Hospital and Auckland DHB has cancelled elective surgery today.

The Health Ministry said Timaru Hospital and Nelson Hospital were discharging patients who could be discharged to make room for earthquake victims.

Three intensive care nurses and three general nurses from Auckland DHB are on standby to go to Christchurch, and several surgeons, anaesthetists and intensive care staff are ready to go if needed.