A night-time curfew is in force across much of quake-ravaged Christchurch, with the grim likelihood of a rising death toll hanging over rescuers desperately searching for survivors.
The number of confirmed dead from Tuesday's 6.3-magnitude quake remains at 75 and more than 300 are missing.
For the first time in its history New Zealand is in a state of emergency. Military and police personnel are patrolling the centre of the city.
Friends and relatives desperately seeking news of their loved ones have been threatened with arrest if they enter the cordoned-off area, which is roughly three square kilometres.
Six people have been arrested for looting, but officials say the exclusion zone has been established to protect non-rescue personnel from the danger posed by collapsed structures.
There have been more than 110 aftershocks since yesterday's quake and the cost has been estimated to be as high as $16 billion - double the damage bill of the quake that hit Christchurch in September.
Rescuers going from building to building looking for survivors have in some cases had to amputate limbs in order to free people from the smouldering ruins.
Hopes were boosted when office worker Ann Bodkin was pulled alive from the flattened Pyne Gould building.
Ms Bodkin, who was lying under her desk, emerged wrapped in blankets to applause from rescue workers.
But there was to be despair for relatives of people believed missing inside the CTV building as police said they were certain those trapped inside were dead.
Police operations commander Dave Lawry says between 80 and 100 people could be missing inside.
"We've got a number of threats - as you can be feeling, continued shocks, the deterioration of the actual site itself as the fire continues to the stage where that pillar's now so weakened we believe that it could collapse on our staff," he said.
"At a certain point I'm not going to risk my staff for people who I believe there is no chance of survivability."
Adding to the danger, a two-block exclusion zone was cleared around the Grand Chancellor Hotel amid fears the 26-storey building may collapse.
One Australian resident has been confirmed dead and grave fears are held for three others that were known to be in the area.
Bravery, heartbreak
There have been tales of bravery and miraculous escapes, and also stories of heartbreak in the wake of the earthquake.
Advertising executive Sven Baker says a snap decision to dive under his desk rather than rush onto the street saved his life as the top two floors of his building tumbled onto the road.
"It was a massive earthquake, just unbelievable. It took you off your feet and the aftermath was just mass destruction," he said.
"I went under a table just as the whole facade of the building collapsed on the street, so I'm pretty grateful for that instinctive decision."
He says the streets were crammed with panicked people.
"It was just like a battle zone, just a street full of dust and screaming people and the smell of gas," he said.
Others were less fortunate. Tom Brittenden saw a woman die with her baby in her arms when she was hit by falling debris in the city's Cashel Street Mall.
He says the woman appeared to have run from a shop in panic when the quake hit. Her baby survived but she was killed instantly.
"We tried to pull these big bricks off [her]... she was gone," he told the Christchurch Press.
Mr Brittenden also had grave fears for a man he helped pull from the rubble who was left in agony after falling from a three-storey building.
"We just went in and pulled the debris off some of the people who were in there and pulled them out," he said.
"We carried one man outside who had fallen three stories from the top of the building, he had serious injuries, a broken pelvis."
Australian help
Prime Minister Julia Gillard said 300 Australian police would be sent to New Zealand and also announced Australia would donate $5 million to the Red Cross Earthquake Appeal.
She said more help was on the way, including a 75-bed field hospital with six surgical, medical and support staff. A 25-strong specialist medical team is also on its way to the stricken city.
Australians already in Christchurch have also been putting their expertise to use.
Dr Sarah Azer was in the city attending a medical conference when the earthquake struck.
"I couldn't just stand there... and do nothing," she said.
"[A colleague and I] just went up to a police officer and we said we're doctors, we want to do something. You let us know where you need us and we'll go."
The police officer sent Dr Azer to the city's cathedral, which is in ruins.
"On the way there there were people lying in the street with cuts. There was a man that looked like he had a pretty serious fracture, probably of both legs, of both bones in his leg.
"We got planks of wood to use as splints; we grabbed towels and t-towels to use as bandages and slings.
"Nothing in our medical training prepares you for this, but all you can do is employ the basics that you're taught in that situation and those basics apply no matter where you are."
Christchurch Airport reopened today and the first international flight out of the city landed in Melbourne Wednesday night.
Matthew Hong, one of the doctors attending a medical conference when the quake hit, says he was forced to leave his belongings behind.
"I made the decision very early on, my luggage is up on floor 24 of the Grand Chancellor Hotel and that's about to collapse, so I decided there was no point in being a hero and going to collect that," he said.