CHRISTCHURCH, New Zealand -- Office workers trapped under their collapsed buildings sent messages to the outside as rescuers with dogs scrambled to save them and dozens of others following a powerful earthquake that killed at least 65 in one of New Zealand's largest cities.
At least 100 people were reportedly buried in rubble as teams worked through the night to try to reach them through slabs of crumbled concrete and twisted metal.
As night fell, thousands of people moved into temporary shelters at schools and community halls in Christchurch. Others, including tourists who had abandoned their hotels, huddled in hastily pitched tents and under plastic sheeting as drizzling rain fell, while the Red Cross tried to find them accommodation.
Tuesday's 6.3-magnitude quake, the second powerful temblor to hit Christchurch in five months, toppled the spire of the city's historic stone cathedral, flattened tall buildings and sent chunks of concrete and bricks hurtling onto cars, buses and pedestrians below.
The quake even shook off a massive chunk of ice from New Zealand's biggest glacier some some 120 miles (190 kilometers) to the east.
Web designer Nathaniel Boehm was outside on his lunch break when the quake struck just before 1 p.m. He saw the eaves of buildings cascade onto the street, burying people below. Others tried to claw their way in, but he didn't see anyone come out.
"People were covered in rubble, covered in several tons of concrete," he said. "It was horrific."
On Tuesday, rescuers, many of them office workers, were seen dragging severely injured people from the rubble of the Pyne Gould Guinness Building, where more than 200 people worked. Screams could be heard from those still inside.
Christchurch Mayor Bob Parker said it was impossible to say how many were still trapped in the rubble citywide, but it was estimated to be more than 100. He added that 200 workers skilled in rescues would search through the night.
"We've got tens of thousands of people just like me who are feeling very scared, very worried and very uncertain of what this night will bring and frankly very, very depressed about what we'll hear tomorrow," Parker told reporters. "It's not going to be good news and we need to steel ourselves to understand that."
Some who were trapped were able to call out using their mobile phones, reaching family, officials and media.
"I rang my kids to say goodbye," said Ann Voss, interviewed by TV3 from underneath her desk where she was trapped in a collapsed office building. "It was absolutely horrible. My daughter was crying and I was crying because I honestly thought that was it. You know, you want to tell them you love them don't you?"
She said she could hear other people still alive in the building and had called out to them and communicated by knocking on rubble.
"I'm not going to give up," she said. "I'm going to stay awake now. They better come and get me."
A search and rescue team was being flown in from Australia to help in the recovery, and Australian Prime Minister Julia Gillard said she had offered New Zealand counterpart John Key any other support he requested.
In the immediate aftermath, dazed, screaming and crying residents wandered the streets as sirens and car alarms blared. With ambulance services overwhelmed, some victims were carried to private vehicles in makeshift stretchers fashioned from rugs or bits of debris.
"It is just a scene of utter devastation," Key said after rushing to the city within hours of the quake. He said the death toll was 65, and may rise. "We may well be witnessing New Zealand's darkest day."
He said eight or nine buildings had collapsed, and others were badly damaged.
A more powerful 7.1 magnitude earthquake hit Christchurch, a city of 350,000, on Sept. 4, but caused no deaths. The latest one may have been deadlier because it was closer to where people live and work, centered 3 miles (5 kilometers) from the city, according to the U.S. Geological Survey. It also may not have been as deep underground.
"The critical issue with this earthquake was that the epicenter was at shallow depth under Christchurch, so many people were within 10 to 20 kilometers (6 to 12 miles) of the fault rupture," said Gary Gibson, a seismologist at Australia's Melbourne University.
About 100 faults and fault segments have been recognised around the region, some as close as 12 miles (20 kilometers) to central Christchurch.
The U.S. Geological Survey said the quake was an aftershock from September's temblor. A strong aftershock in December caused further damage to buildings.
The city was still rebuilding from those temblor when Tuesday's quake hit.
Known in New Zealand as the Garden City, Christchurch on the country's South Island exudes the heritage of its 19th century English founders. A shallow river, the Avon, winds through the downtown that is traversed by historic tram lines and dotted with Gothic architecture, parks and sidewalk cafes. It is a popular destination for foreign tourists and students.
The multistory Pyne Gould Guinness Building, housing more than 200 workers, collapsed and an unknown number of people were trapped inside. Rescuers, many of them office workers, dragged severely injured people from the rubble. Many had blood streaming down their faces. Screams could be heard from those still trapped.
About a dozen visiting Japanese students were among those feared trapped in the rubble of the Canterbury Television building. Some of the students called their parents back home to say they were in a collapsed building, while one of their teachers was able to send an email, Japanese officials said.
One student from the Toyama College of Foreign Languages remained trapped, while 11 were unaccounted for and could still be in the building, said the official from Toyama Prefecture, who would not provide his name because he was not authorized to give public statements. Eight students and two teachers from the school had been freed from the wreckage, he said.
The earthquake knocked out power and telephone lines and burst pipes, flooding the streets with water. Firefighters climbed extension ladders to pluck people trapped on roofs of office towers to safety. Plumes of gray smoke drifted into the air from fires burning in the rubble, and helicopters used giant buckets to drench them with water.
Two large aftershocks -- one magnitude 5.6 and another 5.5 -- hit the city within two hours, and officials warned people to stay away from damaged buildings because of the danger of further collapses.
A U.S. delegation of 43 government, business and community leaders was in Christchurch on Tuesday for a United States New Zealand Partnership Forum meeting. All were thought to be safe.
Nine U.S. Congressmen attending the meeting were reported to have left the city before the quake struck.
Tour guides at the Tasman Glacier in the Southern Alps say the quake shook some 30 million tons of ice to off the glacier, forming icebergs in the lake. The falling ice created waves up to 11-feet (3.5-meters) high, which swept up and down the lake for 30 minutes.
The Christchurch airport, initially closed, was reopened Tuesday to emergency flights, and airport officials said domestic flights would resume on Wednesday.
New Zealand's worst earthquake was one that struck in 1931 at Hawke's Bay on the country's North Island, which killed at least 256 people.
Jeff Peters, who runs a luxury motel in Christchurch about 750 meters from the cathedral, said the earthquake sent microwave ovens, plates and cups in his guest rooms flying.
"Sure we've come back from the last one, but what do we do now?" he said. "Because so much of the city has been destroyed."
Associated Press writers Steve McMorran and Ray Lilley in Wellington, New Zealand, Sean Yoong in Kuala Lumpur, Malaysia, and Jay Alabaster and Tomoko Hosaka in Tokyo contributed to this report.