10,000 homes in Christchurch will have to be demolished after force of quake 'liquified' ground underneath city

* 166 confirmed deaths, but rescuers are still pulling bodies from the rubble
* 260,000 tons of silt already remove after quake 'liquified' rock under city
* Parts of Christchurch will have to be abandoned and modular housing brought in for those left homeless

At least 10,000 homes in Christchurch will have to be demolished because of damage caused by last month's earthquake, Prime Minister John Key said today.

Parts of the city, on New Zealand's south island, will have to be abandoned altogether after the magnitude 6.3 quake caused massive structural damage.

The epicentre of the quake struck within three miles of the city and close to the surface on February 22.

Damage: A car lies under rubble outside the Rugby World Cup venue AMI Stadium

Mourning: Rescue team mebers from Japan Disaster Relief Team hold a moment of silence near the collapsed CTV building. Japanese students were trapped inside a foreign language school in the building

Shattered: A steel frame supports the front of Christchurch Cathedral after it suffered serious damage

It has caused 166 confirmed deaths so far, but that figure will rise as rescuers continue to search for bodies trapped in the rubble of buildings.

Earthquakes can cause sections of earth to liquefy and push up to the surface as watery silt, a process known as liquefaction.

In Christchurch, 260,000 tons of silt have already been scraped away.

Mr Key said: 'There are some parts of Christchurch that can't be rebuilt on.

'The liquefaction damage from the... earthquake is so great and the land damage... is so significant we can't remediate it.'

Mr Key said that 10,000 houses would have to be demolished in the city, including 3,300 that were damaged by an earlier magnitude 7.1 quake on September 4.

That quake was deeper and further away, and did not cause any deaths or as much damage.

Several hundred central city commercial buildings will also have to be bulldozed.

Mr Key said: 'Potentially there are some... areas of Christchurch which will need to be abandoned and we will have to provide other alternatives for people to live in because the land has been so badly damaged we can't fix it - certainly not in a reasonable time frame.'

Modular houses will be brought in to provide temporary accommodation for some of the many thousands left homeless, many of whom will have to abandon their shattered homes and land.

A national memorial service is planned for March 18, and Mr Key said the open-air service in a city park is expected to attract 100,000 people.

Work crews are still clearing rubble from the earthquake, which badly hit the downtown area and cut off water and power across the city.

Almost all electricity supplies have been restored, but residents are being told to boil tap water because of the risk of contamination.

Officials say some 70,000 people - one-fifth of the city's population - have left as a result of the quake.

Repairs: A supermarket in Christchurch is littered with food and debris after the 6.3-magnitude quake