New Zealand authorities have given up hope of finding any more survivors from last week's earthquake.

The head of the civil defence said there had been no live rescues since last week and the grim reality was that no more people would be found alive.

"As time has gone on the chances of finding others alive has diminished. Sadly there comes a point where the response effort has to shift from rescue to the recovery of bodies, and regrettably we have reached that point," said John Hamilton.

Seventy people were pulled out alive from levelled buildings in the city, when the quake struck at a time when the centre was full of lunching office workers and shoppers.

The confirmed death toll is 161, with police estimating that the final toll may be as high as 240, making it the second worst natural disaster after the 1931 Napier earthquake which claimed 256 people.

The local mayor said the news made it a "terrible" day for Christchurch.