One of New Zealand's biggest cities lay in ruins on Tuesday after a powerful earthquake toppled buildings and churches on a busy weekday, killing at least 65 people in the country's worst natural disaster in decades. The quake even shook a massive chunk of ice from New Zealand's biggest glacier, some 192 km to the east of Christchurch, where most of the damage was reported.

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 on Tuesday night. Rescue crews with sniffer dogs fanned out across the city in search of survivors, some of whom were able to send text messages or make phone calls from under the wreckage.

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.

“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 buildings collapsed in on themselves and streets were strewn with rubble.

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 some victims clutching bleeding wounds were carried to private vehicles in makeshift stretchers fashioned from rugs or bits of debris.

More In: International | News