Death toll rises to 75 following New Zealand quake

More than 500 search and rescue personnel, police, fire service staff, soldiers and volunteers worked throughout the night to find survivors trapped under the rubble, many using only their bare hands.

"There is incredible carnage right throughout the city," Police Superintendent Russell Gibson said. "There are bodies littering the streets, they are trapped in cars and crushed under rubble."

"We are getting texts and tapping sounds from some of these buildings and that's where our focus is," he added.

"It's quite amazing, we have some people we've pulled out and they haven't got so much as a scratch on them, we've had other people where we've had to amputate limbs to get them out."

Asked how many may still be trapped, Supt Gibson said: "It could be another 100 - it could be more."

So far, more than 300 people are still missing despite how forty-eight were pulled out from collapsed buildings alive overnight.

"The situation is that we don't believe this site is now survivable," said police area commander Inspector Dave Lawry near the remains of the Canterbury Television building. "It was a hard choice and my heart goes out to all the families."

He said rescuers now needed to concentrate their resources elsewhere in areas where survivors were more likely to be found.

About 100 people are believed to be inside. Earlier, the head of the fire service denied reports that 15 people trapped inside had been rescued.

The building housed a language school and Inspector Lawry said some foreign students would be among the dead there.

At the Pyne Gould Guinness building, office worker Ann Bodkin was pulled out alive on Wednesday afternoon, after being trapped for more than 24 hours, and was reunited with her waiting husband.

The authorities have also imposed a night-time curfew in the worst-affected areas of the city.

The earthquake struck at a shallow depth of 5km (3.1 miles) on Tuesday lunchtime, when the South Island city was at its busiest.

It was Christchurch's second major tremor in five months, and New Zealand's deadliest natural disaster in 80 years.

Later, officials said a total of 300 people were believed to be missing, but details are unclear and officials are currently trying to refine that list. Some people may simply not have been able to contact friends and relatives.

The ministry of civil defence said 22 people alone were missing in Christchurch Cathedral, which lost its spire and a section of roof. Police say there has been no sign of life from underneath the rubble.