At least 65 people have died in the 6.3 magnitude earthquake which struck Christchurch at 12.50pm today, causing widespread devastation in the city.
Although lower in magnitude than the September 4 quake last year, today’s jolt has caused more damage, with Prime Minister John Key describing the situation as “New Zealand’s darkest day”.
Mr Key has told reporters that the death toll from today's magnitude 6.3 earthquake stood at 65 and was likely to rise.
Today’s big shake was located at a depth of 5km while the Sept 4 quake was close to 33km deep.
Speaking from Christchurch after flying down this afternoon, Mr Key told One News New Zealanders should be assured the Government was doing everything it could.
It is not known at this stage whether there were any Indians among the fatalities.
There were 180 police on the ground, a further 200 were on the way and 350 military were already in Christchurch with another 250 to arrive soon.
The Government had accepted offers of specialist help from Australia and US.
"I don't think we can go past the fact that we may well be witnessing New Zealand's darkest day."
The latest "very fluid" advice was that the death toll 65, "and that may rise".
"It's an absolute tragedy for this city, for New Zealand, for the people we care so much about and it's a terrifying time for the people of Canterbury.
Christchurch mayor Bob Parker says: "As daylight comes tomorrow we need to prepare ourselves for what is likely to be significant numbers of casulaties."
Search and rescue teams are to work throughout the night looking for survivors following today's massive Christchurch earthquake, Civil Defence director John Hamilton says.
"We have to be prepared to accept that it is going to be a heavy toll,'' Mr Hamilton said.
He could not say how many people were trapped in buildings, saying the information was "patchy".
"There could well be people who are stuck in buildings overnight. I can't confirm, but I would expect that's in all probability the case."
Mr Hamilton said an urban search and rescue team from Australia was on its way, and was expected to arrive after midnight.
The Pyne Gould Guinness building was one of the worst hit, with at least 30 people said to be trapped in the rubble.
Christchurch mayor Bob Parker said the damage was much more severe than in the great 7.1 quake almost six months ago.
"The city centre is like a war zone and damage is immense.
"Everybody needs to understand that this is going to be a day of very black news," the mayor said.
Earlier today, residents reported were bodies lying in the streets of Christchurch.
Police said fatalities had been reported at several locations and that two buses had been crushed by falling buildings. Christchurch mayor Bob Parker has declared a state of emergency.
Christchurch resident Jaydn Katene told the NZ Herald: "We've had friends in town call us and say there are just bodies lying around; lots of dead bodies outside shops just lying there just covered in bricks.
"When it hit we were knocked to our feet. Everything in the house fell down, nothing was left still standing. There's more damage than the first earthquake, the roads are completely torn up; sewage coming up and flooding. It's crazy."