New Zealand quake kills at least 65

About 120 survivors have already been rescued from the rubble, but the death toll is expected to rise following the second strong quake to hit the city of almost 400,000 people in five months.

"We may well be witnessing New Zealand's darkest day...The death toll I have at the moment is 65 and that may rise," said New Zealand Prime Minister John Key, who had flown to his home town of Christchurch, where he still has family.

Tuesday's 6.3 magnitude quake struck at lunchtime, when streets and shops thronged with people and offices were still occupied. It was New Zealand's most deadly natural disaster for 80 years.

Rescuers, working under lights in rain, focused on two collapsed buildings: a financial-services office block whose four stories pancaked on top of each other, and a TV building which also housed an English-language school.

About a dozen Japanese students at the school were believed to be missing, an official in Japan told Reuters, while public broadcaster NHK said several other students from another group in the building were also unaccounted for.

Trapped survivors could be heard shouting out to rescuers from the TV building. Local media say as many as a dozen or more people could still be inside. Relatives of those feared trapped kept a vigil outside the building as rain began to fall.

"All of our energy tonight is really focused on the need to rescue people," said Christchurch Mayor Bob Parker, estimating 120 people had been pulled out of rubble or rescued so far.