Updated

CHRISTCHURCH, New Zealand -- Rescuers used their bare hands, dogs, and heavy machines Wednesday in an urgent search for survivors still trapped in crumbled buildings more than 24 hours after an earthquake devastated one of New Zealand's largest cities.

The confirmed death toll from Tuesday's magnitude-6.3 quake rose to 75, and officials said it was almost sure to climb further. Some 300 people were listed as missing.

Cheers broke out when an emergency team pulled a woman from the twisted metal and shattered concrete of one of the worst-hit buildings in Christchurch, while police announced they had lost all hope of finding survivors in another major wreckage.

Parts of the city of 350,000 people lay in ruins, and all corners of it were suffering cuts to water supplies, power and phones.

The city was virtually shut down Wednesday, and police announced a nighttime curfew in a cordoned-off area of downtown saying buildings were at risk of crumbling in the afterschocks still rumbling through the city. Anyone on streets after 6:30 p.m. would be arrested, police said.

Prime Minister John Key declared a national state of emergency as hundreds of soldiers, police and other emergency workers -- including specialist teams from the U.S. and other countries -- rushed to Christchurch as aftershocks continued to strike the area.

One of the city's tallest buildings, the 27-floor Hotel Grand Chancellor, was in imminent danger of collapsing, with one corner having sunk lower in the ground and the facade showing major buckling, Fire Service commander Mike Hall said.

Authorities emptied the building and evacuated a two-block radius, holding back residents with a police rope. Real estate salesman David Rankin, 50, stood gazing at the hotel where he said he was supposed to be having a lunch meeting.

Rankin said he was amazed by the ubiquitous ruins and dust unleashed by the quake, "like a war zone, like a bomb had gone off."

The immediate focus was on about a dozen buildings downtown where finding survivors was still a possibility. In other places, rubble was being left untouched -- even if bodies were thought buried there -- until the urgency of the survivor search passes.

Rescuers pulled Ann Bodkin free from the debris of the Pyne Gould Guinness building, where she was quickly reunited with her husband who had anxiously watched the painstaking rescue.

Giant sunbeams burst through the grey, drizzly weather as she emerged from the wreckage, prompting one official to say, "They got Ann out of the building and God turned on the lights," Mayor Bob Parker recalled moments after Bodkin was whisked to safety.

In contrast, the mood was dismal near the smoldering remains of the Canterbury Television building, where brother and sister Kent and Lizzy Manning sat on a rain-sodden patch of grass Wednesday waiting for news of their mother, Donna, a television presenter who they hadn't heard from since the quake.

"My mum is superwoman, she'd do anything," said Lizzy Manning, 18, with tears running down her face.

At that moment, a police official knelt down beside the pair.

"I have some horrible news ...," the officer began, before telling the siblings that there was no hope for anyone left trapped inside the building.

The siblings bowed their heads and wept. Their father rushed over and enclosed them in an embrace.

Officials pointed thermal cameras into the wreckage, and sniffer dogs clambered on top looking for signs of life. Officials at one point said they believed they had found a pocket of at least 15 people buried alive in one building -- but the report turned out to be false.

Parker, the Christchurch mayory, said early Wednesday that 120 people were rescued from wrecked buildings as teams worked through the night, while more bodies were also recovered. About 300 people were still unaccounted for, but this did not mean they were all still trapped, he said.

Some survivors emerged without a scratch, while others had to have a limb amputated before they could be freed.

"There are bodies littering the streets, they are trapped in cars, crushed under rubble and where they are clearly deceased our focus ... has turned to the living," police Superintendent Russell Gibson said.

Military units patrolled near-empty streets disfigured by the huge cracks and canyons created in Tuesday's earthquake, the second powerful temblor to hit the city in five months. The quake toppled the spire of the city's historic stone cathedral and flattened tall buildings.

Parker said an unknown number of people, possibly 20 or more, were believed to have been inside the cathedral tower -- climbing it was a popular activity for tourists.

The quake struck just before 1 p.m. local time on Tuesday, when the city was thronging with workers, tourists, and shoppers. The quake was not as powerful as a magnitude 7.1 temblor that struck before dawn on Sept. 4 that damaged buildings but killed no one. Experts said Tuesday's quake was deadlier because it was closer to the city and because more people were about.

Mall worker Tom Brittenden told of how he had helped pull victims from the rubble in the immediate aftermath of the quake, including a woman who died cradling her baby in her arms.

"There was a lady outside we tried to free with a child," Brittenden told National Radio. "A big bit of concrete or brick had fallen on her and she was holding her child. She was gone. The baby was taken away."

Christchurch's airport reopened for domestic flights Wednesday, and military planes were brought in to fly tourists to other cities.

Thousands of people in the city, including tourists who had abandoned their hotels, spent the night in temporary shelters at schools and community halls.

Officials told people to avoid showering and even flushing their toilets, saying the damaged sewer system was at risk of failing.

Downtown was cordoned off to keep people away from wobbly buildings and to give free-rein to rescue workers and maintenance crews. Officials urged residents elsewhere to stay off the streets unless their journeys were absolutely necessary. All schools in the city were closed until further notice.

Denis Torrey, president of the city's junior school principals' association, said there were no reports of students or teachers being harmed in the quake, though some schools were badly shaken.

"It was very scary, there were some staff thrown to the ground," she told National Radio. "The teachers very calmly gathered children into groups. There were lots of group hugs and lots of comforting going on."

More than 400 rescue workers were joining the search, including teams from Australia, Singapore, Taiwan, the United States and Britain.

New Zealand's worst earthquake struck in 1931 at Hawke's Bay on the country's North Island, killing at least 256 people.