Kaikoura has less than 24 hours of drinking water left, while vital supplies are also diminishing.
However, Civil Defence says restoring water supplies and ensuring bottled water is flown into town remains its top priority as many people remain homeless from Monday morning's deadly earthquake.
Kaikoura Mayor Winston Gray also reassured tourists that it was also their mission to get them evacuated as quickly as possible.
Of the approximate 4500 people in town, about 1000 were tourists, he said.
As at 1pm on Tuesday, 160 had been flown out by helicopter and the airlift by emergency services and defence personnel continued amid more strong aftershocks on Tuesday, a day after a powerful earthquake killed two people.
The 7.8-magnitude tremor struck just after midnight on Sunday, and cutting road and rail links throughout the northeast of the South Island.
The town of Kaikoura was completely cut off by massive landslips.
As aftershocks continued to rattle the region, emergency services cordoned off streets in Wellington and evacuated several buildings due to fears one of them might collapse.
Wellington Mayor Justin Lester said the vacant building appeared to have suffered structural damage when the land it was on subsided in the quake. A fire service official said a major structural beam had "snapped like a bone".
In Kaikoura, Civil Defence controller John Mackie said specialist engineers had arrived and others were on the way to help out.
Sorting water was his mission: ``Clean, fresh drinking water. There's about a day's storage left.''
Another goal was to set up water drinking stations around the town.
Four defence force helicopters flew in to the town on Tuesday morning and the Navy's multi-role vessel HMNZS Canterbury was heading to the area, Air Commander Darryn Webb, acting commander of New Zealand joint forces, told TVNZ.
"The priority today is the airlift operation," he said. "We're looking to do as many flights as we can out of Kaikoura today . . . to move approximately 200 of those tourists and residents south."
Around 1200 tourists were stranded in the town, officials said, and other emergency services were also using helicopters to fly in supplies and fly out those who wanted to leave.
Road access would be restored to Kaikoura within days, Transport Minister Simon Bridges said on Tuesday.
But repairing State Highway 1 and the rail lines either side of the township would take months and was likely to cost hundreds of millions, he said.
Speaking to reporters at Parliament, Bridges said the New Zealand Transport Agency was working around the clock to fix bridges on a local, inland road, previously known as State Highway 70, into Kaikoura.
``What I can say, for the people of Kaikoura, is that we are talking about days not months, and they are working as fast as they can.''
Mark Solomon, a leader of Ngai Tahu, which has tourism and fisheries businesses around Kaikoura, said the local marae had received 1000 people since Monday morning. Many slept overnight in the communal hall or in vehicles outside.
The tribe had fed them with crayfish, a delicacy for which the South Island town is famous. With no power, the tanks that hold the expensive crustaceans had stopped pumping.
"It's better to use the food than throw it in the rubbish so we sent it up to the marae to feed people," Solomon told Reuters by phone.
Meanwhile, China chartered four helicopters to evacuate around 40 nationals, mostly elderly and children, from Kaikoura late on Monday, said Liu Lian, an official at the Chinese Consulate in Christchurch.
Other tourists said they planned to continue their trips, and travel agencies said they had not noticed a drop-off in bookings, easing concerns about a major hit to the sector, New Zealand's biggest export earner.
Gale-force winds and rain were hampering recovery efforts, and hundreds of aftershocks continued to rock the region. A 5.4 tremor was among the bigger aftershocks and was felt strongly in Wellington.
The 7.5-magnitude quake hit near Hanmer Springs at 12.02am on Monday, leaving thousands of people stranded in the seaside town which was still without water, sewerage systems and phone reception.
The quake destroyed historic farm homesteads, sent glass and masonry toppling from buildings in the capital Wellington and cut road and rail links throughout the northeast of the South Island. There had been more than 860 aftershocks, GeoNet said.
Civil Defence estimated 80,000-100,000 landslides had been caused by the quakes.
New Zealand media reported that three cows filmed stranded on a small patch of grass surrounded by landslips near Kaikoura had been rescued by a farmer.
Finance Minister Bill English reiterated Mr Key's estimate that the cost of quake repairs would be in the "billions''. He said the Earthquake Commission disaster fund was depleted, but a Government guarantee would mean all insurance claims were met.
Mr English said not only were South Island roads badly damaged, but also the ports at Picton and Wellington.
Mr Key said the wild weather in Wellington was causing "yet another complicating factor to the aftermath of the earthquakes''.
It was making travel difficult in Wellington and hampering efforts to airlift people out of Kaikoura, he said.Mr Key said the Government's other priority was helping small businesses in Kaikoura, which had immediate and possibly medium-term needs.
Acting Civil Defence Minister Gerry Brownlee said New Zealand had accepted an offer of two US Navy helicopters from the destroyer the USS Sampson, as well as an offer of help from the Japanese military.
It was hoped an inland road to Kaikoura from the south could be reopened by the weekend, he said.
Workers began returning to office buildings in Wellington's business district, which was closed off on Monday while the city council assessed the risk to buildings.
Several blocks were damaged by the tremor, including the offices of Statistics New Zealand, which said the release of economic data had been halted and that it would be months before it could use the building.
Two people died as a result of Monday's quake, which also triggered tsunami warnings, sending many residents along the South Island's east coast fleeing to higher ground.
One man died and two women were pulled from the rubble in Kaikoura when the historic Elms Homestead collapsed, and a Mt Lyford (inland from Kaikoura) woman reportedly died from a medical event while she was evacuating her home.
New Zealand's Geonet measured Monday's main quake at magnitude 7.5, while the US Geological Survey put it at 7.8. Seismologists said the quake actually appeared to be two near simultaneous tremors which shook much of the country for around two minutes.
New Zealand lies in the seismically active "Ring of Fire", a 40,000-km arc of volcanoes and oceanic trenches that encircles much of the Pacific Ocean. Around 90% of the world's earthquakes occur in this region.
Homes burgled
Since Monday's quake, police have received 19 reports of burglaries at Canterbury properties. One family's Christchurch home was looted after they fled to safety. More than $20,000 had been raised online for them by last night.
"This sort of offending really scrapes the bottom of the barrel,'' Canterbury district commander Superintendent John Price said.
Extra officers have been sent from Auckland and Blenheim to Kaikoura to provide support.
- Reuters, NZ Herald, NZME.
