CHRISTCHURCH - New Zealand said Saturday one-third of Christchurch's city centre faces demolition after an earthquake killed at least 123, and warned it may be unable to host the Rugby World Cup.

Quake aftermath Click on thumbnail to view. View more photos here

Earthquake Recovery Minister Gerry Brownlee urged the stricken city to be "realistic" about holding World Cup matches in September and October after the 6.3-magnitude quake caused widespread damage, including to the rugby stadium.

"To lose the Rugby World Cup from Christchurch would be a massive blow," Brownlee told TVNZ.

"I don't want to see it happen but we've got to be realistic about the prospect."

Rugby-mad Christchurch, New Zealand's second-largest city, is one of the main venues for the seven-week competition, and is slated to hold two quarter-finals on October 8 and 9. But Tuesday's quake reduced much of the city centre and some suburbs into ruins. Although Stadium Christchurch has only minor damage, the pitch has been hit by liquifaction, when soil becomes a quagmire due to the ground's shaking.

Stadium officials also reported serious damage around the venue, which is just two kilometres (just over a mile) from the rubble-strewn city centre - where Christchurch's biggest hotel is tottering and in danger of collapse. On Saturday, engineers said as much as a third of the central district, where office buildings folded like packs of cards and entire streets lost their shop frontages, may be demolished and rebuilt.

"We've collected some data over the past couple of days and it's looking like about one-third of the buildings (would be condemned)," Auckland University structural engineer Jason Ingham told TVNZ.

"We will have to prune this city and we'll have to prune it hard," city mayor Bob Parker told Sky News. "Entire blocks are going to have to go." Earthquake minister Brownlee said the centre may be closed for months.

Police raised the creeping death toll to 123 with more than 200 missing. Officials said the toll could rise sharply later, although some of the dead are likely to be included among those still unaccounted for.

Prime Minister John Key, who was raised in Christchurch, was due to visit families of the dead or missing Saturday on his latest trip to the disaster zone. Power has now been restored to most of the city but many of its 390,000 residents are without water and relying on supplies brought by tanker.

Officials said more than 62,000 homes have no water supplies and 100,000 properties are without sewerage, while 800 portable toilets will soon be in place to help ward off the threat of disease.

Despite a major international search operation involving some 700 specialist personnel, no signs of life have been detected in the quake wreckage since Wednesday, when the last of about 70 survivors was rescued.