Officials say 71 bodies have been recovered so far but more are known to still be under the rubble.

Foreign rescue workers are arriving to join the search effort, amid warnings that time is running out for survivors. No-one was found alive overnight.

The 6.3 magnitude quake is the country's biggest disaster in 80 years.

The New Zealand Prime Minster, John Key, has declared a national state of emergency and authorities have imposed a curfew.

For a second night rescue teams in Christchurch are continuing their painstaking search for those lost in the wreckage.

There have been moments of exhilaration when survivors have been pulled from office blocks that have been utterly shattered.

Emergency workers concede, though, that it's likely their grim task will soon begin to reveal more bodies.

More than 36 hours after the earthquake struck, more details are emerging of what the New Zealand Prime Minister John Key has called a "ruthless act of nature".