GNS Science initially reported the quake as magnitude 7.4, but later downgraded it after re-examining quake records. The U.S. Geological Survey, in America, measured the quake at 7.0.

Panicked residents in their pajamas ran into the streets of the southern city of Christchurch after the pre-dawn quake, residents said. There were just two reports of serious injuries. Looters broke into some damaged shops in Christchurch, police said.There were also reports of some people trapped in damaged buildings though none appeared to be crushed by rubble and a few looters broke into some of the damaged shops in the city of 400,000, authorities said.

Chimneys and walls had fallen from older buildings, roads had been blocked, traffic lights out and power, gas and water supplies disrupted .Christchurch Mayor Bob Parker declared a state of emergency four hours after the quake rocked the region, warning people that continuing aftershocks could cause masonry to fall from damaged buildings.

"The fronts of at least five buildings in the central city have collapsed, and rubble is strewn across many roads," Christchurch resident Angela Morgan told The Associated Press. "There is quite significant damage, really, with reports that some people were trapped in damaged houses."

Army troops were on standby to assist, Minister of Civil Defense John Carter said, as a state of civil emergency was declared.

"I think we've been extremely lucky as a nation that there's been no fatalities," Carter told reporters, though he said infrastructure damage was major. Earthquake and insurance specialists would give government an initial damage assessment within 48 hours, he said.

Parker said the quake caused "a lot of damage to our key infrastructure such as water, waste water (sewerage) systems ... but the most important thing is that there has been no loss of life."Fewer than 10 a year do any damage.