Christchurch has woken on Wednesday from what a local business leader calls the nightmare that didn't happen in September.

Tuesday afternoon's 6.3 earthquake has shattered the New Zealand South Island's largest city, leaving an official death toll of 39 that is certain to climb as more bodies are found beneath the rubble of destroyed and damaged buildings.

Prime Minister John Key said on Tuesday evening that the death toll was 65, but Superintendent Dave Cliff of the Christchurch police told Radio New Zealand at 9.20 am on Wednesday that the confirmed toll at this stage is 39.

That figure is based on definite identification of the deceased.

Separately, Superintendent Russell Gibson has said 38 bodies are in the mortuary and dozens more litter the streets, trapped in cars and under rubble.

Key said Cabinet will consider on Wednesday morning whether to declare the quake a national state of emergency.

Hundreds of search and rescue personnel, fire service staff, army personnel and volunteers worked under floodlights through the night to get to those who are still trapped -- some of whom have been texting for help.

Police said 100 people are still thought to be trapped. But more than 100 have been pulled out alive.

There is no official list of who is missing yet, so Civil Defence does not have a figure for the number of people trapped.

Hundreds of displaced people spent the night in specially set up welfare centers at Hagley Park North, Addington Raceway and Burnside High School, and Civil Defence aims to open more center throughout Wednesday.

Christchurch Mayor Bob Parker said the central city will be shut down on Wednesday and will stay that way for a significant amount of time.

Parker said a cordon manned by military personnel is in place around the four avenues surrounding the central area.

The Ministry of Education said all schools in Christchurch are closed until further notice.