CHRISTCHURCH, New Zealand (AP) -- A powerful earthquake struck one of New Zealand's biggest cities Tuesday at the height of a busy workday, toppling tall buildings and churches, crushing buses and killing at least 65 people in one of the country's worst natural disasters.
It was the second major quake to hit Christchurch, a city of 350,000, in five months, though Tuesday's 6.3-magnitude temblor caused far more destruction than a stronger September quake that struck before dawn on a weekend. More than 100 people, including as many as a dozen visiting Japanese students, were thought to be trapped in the rubble as darkness - and drizzling rain - fell Tuesday night.
"It is just a scene of utter devastation," Prime Minister John 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."
The spire of the city's well-known stone cathedral toppled into a central square, while multistory buildings collapsed in on themselves and streets were strewn with bricks and shattered concrete.
Sidewalks and roads were cracked and split, while thousands of dazed, screaming and crying residents wandered through the streets as sirens and car alarms blared. Ambulance services were quickly overwhelmed, and groups of people helped victims clutching bleedings wounds, and others were carried to private vehicles in makeshift stretchers fashioned from rugs or bits of debris.
Nathanael Boehm, a web designer, said he was standing near a tram track when the quake struck just before 1 p.m., sending the eaves of buildings cascading onto the street below.
"It was horrific. People were covered in rubble, covered in several tons of concrete," Boehm said, adding that he believed some of them had been crushed to death.
Christchurch Mayor Bob Parker declared a state of emergency and ordered people to evacuate the city center. He said it was impossible to say how many people were trapped in the rubble, but that it was estimated to be more than 100.
"The government is willing to throw everything it can in the rescue effort," Deputy Prime Minister Bill English said. "Time is going to be of essence."
Troops were deployed to help people get out and to throw up a security cordon around the stricken area, and residents throughout the city were urged to stay home or with neighbors and conserve water and food.
The airport was closed, and Christchurch Hospital was briefly evacuated before reopening. Power and telephone lines were knocked out, and pipes burst, flooding the streets with water. Some cars parked on the street were buried under rubble.
Police said reports of fatalities included people in two buses that had been crushed by falling buildings.
During hours of chaos in the city, people dug through rubble with their hands to free people trapped. Firefighters climbed extension ladders to pluck people stranded on roofs to safety. A crane lifted a team of rescuers on a platform to one group of survivors in a high-rise. Plumes of gray smoke drifted into the air at several points around the city from fires burning in the rubble.
Parker said rescue teams including sniffer dogs were fanning out across the city and would work through the night.
Officials had established relief centers in schools and community halls, where food was being served to thousands of sheltering people and donated blankets were being handed out. In at least one park in the city, people - many of them tourists who had abandoned their hotels - huddled in hastily pitched tents and under plastic sheeting. The Red Cross was working to secure accommodation for them.
Key, who held an emergency Cabinet meeting then rushed to the stricken city to observe the scene, said eight or nine buildings had collapsed, and others were badly damaged.
Some of those stuck were thought to be visiting Japanese students who called their parents back home to say they were in a collapsed building, a Japanese official said.
Two students 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 declined to 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.
Others were also 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."
Gary Moore said he and 19 other colleagues were trapped in their twelfth floor office after the stairwell collapsed in the quake.
"We watched the cathedral collapse out our window while we were holding onto the walls," Moore said. "Every aftershock sends us rushing under the desks. It's very unnerving but we can clearly see there are other priorities out the window. There has been a lot of damage and I guess people are attending to that before they come and get us."
The multistory Pyne Gould Guinness Building, housing more than 200 workers, collapsed and an unknown number of people were trapped inside. Television pictures showed rescuers, many of them office workers, dragging severely injured people from the rubble. Many had blood streaming down their faces. Screams could be heard from those still trapped.
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.
The U.S. Geological Survey said the temblor was centered 3 miles (5 kilometers) from the city at a depth of 2.5 miles (4 kilometers). Two large aftershocks - one magnitude 5.6 and another 5.5 - hit the city within two hours. It was felt across a large part of the South Island, and caused damage in nearby towns. The extent of damage elsewhere wasn't immediately clear.
"When the shaking had stopped I looked out of the window, which gives a great view onto Christchurch, and there was just dust," said city councilman Barry Corbett, who was on one of the top floors of the city council building when the quake struck. "It was evident straight away that a lot of buildings had gone."
The USGS said the latest quake was part of the "aftershock sequence" following the 7.1 magnitude earthquake on Sept. 4 last year. That quake wrecked hundreds of buildings, inflicted an estimated 4 billion New Zealand dollars ($3 billion) in damage, but caused no deaths.
A strong aftershock in December caused further damage to buildings. The city, considered a tourist center, was still rebuilding from those quakes when Tuesday's temblor hit.
The USGS said the latest quake hit "significantly closer to the main population center of Christchurch" than the September quake, which was centered 25 miles (40 kilometers) west of city.
"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.
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.
Associated Press writers Steve McMorran and Ray Lilley in Wellington, New Zealand, Sean Yoong in Kuala Lumpur, Malaysia, and Jay Alabaster in Tokyo contributed to this report.