The Prime Minister says initial Treasury modelling has put the cost of the Canterbury earthquake at $2 billion.
John Key was speaking after flying over areas worst hit by the Saturday morning 7.1 quake with Christchurch Mayor Bob Parker.
Describing it as New Zealand's worst natural disaster since the Inangahua earthquake in 1968, he says parts of the city look as though they've been through a tumble-drier.
Mr Key says insured householders with damaged homes will be well covered by the Earthquake Commission, which has assets of $15 billion.
In what he says is a sign of solidarity with the people of the region, Mr Key flew to Christchurch on Saturday afternoon, saying that the Government will not let residents suffer alone and any required support will be given.
Mr Key flew from Whenuapai base in Auckland in an Air Force Hercules with 20 search and rescue team members on board. On the way south, the plane picked up more rescue personnel at Ohakea and several Cabinet ministers in Wellington.
At least 100,000 claims likely
An EQC executive, Ian Simpson, says that at least 100,000 individual claims are likely, but that the commission is well placed to handle the surge, with $6 billion worth of assets and another $2.5 billion of re-insurance able on call.
Mr Simpson, who planned to travel to Christchurch with insurance industry executives to view the damage, says people should start assessing damage to their properties over the next few days and lodge claims.
He says claims should be lodged with EQC before private insurers.
People should keep as much physical evidence of damaged belongings as they can, Mr Simpson says, plus receipts from any sanitary repair work required.
More insurance assessors on job
The Insurance Council's chief executive, Chris Ryan, says it will not be able to estimate the cost of the damage until early next week but insurers are doubling their numbers in call centres and bringing in more assessors.
Mr Ryan says people should concern themselves with their safety and hold off filing claims until later. Those who are evacuating their properties should ensure as far as they can that they are secure.
Mr Ryan adds, however, that it is perfectly understandable if a house is badly damaged and unable to be secured.