UPDATE: SIXTY-FIVE people died in a powerful earthquake that ripped Christchurch apart today and the toll is expected to rise.

Prime Minister John Key announced tonight that "at least 65 people have lost their lives" and noted the rescuers were still scrabbling through the ruins of collapsed buildings looking for injured and trapped survivors - and bodies.

The death toll is already the second highest in a New Zealand earthquake - outranked only by the 286 people who died in the violent 7.9 1931 Hawke's Bay quake, whose 70th anniversary was marked earlier this month.

Police have reported "multiple fatalities" at several locations in the downtown area, including where two buses were crushed by falling buildings.

Today's shake, measured at 6.3 on the Richter Scale, followed the massive 7.1 tremor on September 4 last year. That one struck in the early hours of the morning and no one was killed.

Today's earthquake jolted the city at 12.51pm, the worst possible time with the central city packed with lunch-hour shoppers, office workers and many school children.

Victims were crushed to death as buildings collapsed, many of them weakened in last year's event.

The quake was not as powerful as the 7.1 that struck in early morning hours of September 4 last year but was much shallower, leading to greater damage.

Scientists put the epicentre at 10km southeast of the city - apparently in the middle of the harbour at Lyttelton, the city's coastal port - at a depth of only 5km.

Radio and television reported damage in the town of Lyttelton was severe.

The Pyne Gould Guinness building, several storeys high, folded up like a pack of cards and rescuers were still trying to find trapped occupants tonight.

Up to 50 people were said to be in the wreckage - alive or dead.

Rescuers were trying to get people out of the Canterbury TV building in Madras Street, while firefighters battled a fire there.

The famous cathedral in the city's downtown square which stood undamaged last September lost its spire today and suffered heavy damage.

Reports that people were in the spire when it tumbled into the church itself and the square outside could not be verified immediately.

Mr Key flew to Christchurch this afternoon and after a quick tour of the city described it as "utterly wrecked", adding "this is an absolute tragedy for Christchurch".

"We may well be witnessing New Zealand's darkest day," he said.

Graphic photographs on television showed blood-splattered survivors scrambling from downed buildings or crawling from under shattered shop verandas that had fallen onto city footpaths.

Crushed cars lined parking spaces, masonry scattered across roads.

Christchurch mayor Bob Parker, lauded for his behaviour and slick civic control in the wake of last year's quake, said the damage today 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," he said.

He declared a state of emergency, adding Christchurch and Canterbury would need help from the rest of the country.

Christchurch Airport closed after today's earthquake and was to remain shut down overnight, open only to emergency flights and aircraft carrying rescuers and medical helpers.

Extra police, armed forces troops and search and rescue teams were heading for Christchurch tonight and the inter-island ferry heading for the South island from Wellington carried a group of 40 police, among them victim-identification specialists.

A 73-strong New South Wales search and rescue team arrived in Christchurch tonight and will go to work at first light tomorrow.

The road tunnel under the Port Hills linking Christchurch and Lyttleton was closed for some hours but was reopened tonight for emergency vehicles.

The earthquake ruptured sewer and water lines, still under repair after last September, and LPG gas lines were shut off after consumers reported leaking gas.

One third of the city was without electricity tonight after the quake brought down lines and poles.

Heavy aftershocks continued to roll across Christchurch tonight, further frightening shocked residents. A 5.0 magnitude jolt hit at 7.43pm local time.

Some reports said the majority of the damage was confined to Christchurch and nearby areas and that rural property had not suffered greatly.

But on the west coast, the face of the immense Tasman Glacier collapsed in enormous chunks into its lake following the earthquake.

"Bodies everywhere"

RESIDENTS are reporting bodies lying in the streets of Christchurch following this afternoon's magnitude 6.3 earthquake.

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 said: "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."

"The elderly are all crying. The next-door neighbours around us were all bawling their eyes out, it was horrible. People can't get out of their houses," said Mr Katene.

"We've seen cars halfway sunken into the road. We've heard there's a bus which is sunken halfway into the road just around the corner.

"Buildings are half-collapsed everywhere.

"It smells horrible. The roads are packed with cars. There aren't enough police or ambulances. Houses are all collapsing. It's pretty shocking; a total warzone."

Aftershocks continue

STRONG aftershocks are continuing to shake Christchurch as police confirm "multiple fatalities" after a 6.3 magnitude quake hit the city this afternoon.

Police said fatalities had been reported at several locations and that two buses had been crushed by falling buildings.

GNS Science said today's 12.51pm quake was centred at Lyttelton at a depth of 5km.

It was followed by a 3.4 magnitude aftershock at 2.3pm, a 4.0 aftershock at 2.39 and a severe 5.5 magnitude aftershock at 2.50pm.

Herald reporter Jarrod Booker said queues of cars could be seen being shaken up and down when the latest aftershock hit.

GNS Science said it was also at a depth of 5km and centred near Lyttelton.

Jarrod Booker said cars stuck in the city's gridlock were being rocked side to side and occupants could be heard screaming.

"Even sitting in a car you can feel continual shaking on a smaller scale than the original quake," he earlier said.

Deaths in Christchurch

THERE have been "multiple fatalities" after a shallow 6.3 magnitude earthquake in Christchurch this afternoon caused buildings to collapse, police have confirmed.

Police said fatalities had been reported at several locations and that two buses had been crushed by falling buildings.

Christchurch resident Jane Smith, who works in the central city, told the Herald a work colleague had just returned from helping rescue efforts after a building facade had collapsed on a bus on Colombo St.

"There's people dead. He was pulling them out of a bus. Colombo St is completely munted."

TV3 reported that a person had died in the Christchurch suburb of Sumner.

Police said there were reports of fires in buildings in the central city and of people being trapped.

Police said all available staff were helping with the rescue operation and the Defence Force had been called in to assist.

Triage centres have been established for the injured at Latimer Square in the central city, Spotlight Mall in Sydenham and Sanitarium in Papanui.

A Herald reporter said that emergency services were struggling to enter the central city and were having to manoeuvre slowly around gridlocked traffic.

"Numerous people" trapped in quake rubble

Numerous people are trapped in Christchurch buildings following a 6.3 magnitude earthquake, the fire service says.

New Zealand's TV3 television showed pictures of people being rescued from the Pyne Gould Guinness building, where the network said 200 people had originally been trapped.

The television footage showed the building had collapsed.

Elsewhere in the city, TV3 said the provincial chambers building had collapsed and people were believed to be trapped inside.

The quake caused more damage than the 7.0 magnitude quake that hit Christchurch last September, a fire service spokesman said.

"The shake has been a lot worse, maybe not in intensity but as far as damage is concerned, and there are numerous people trapped," he told Radio New Zealand.

Meanwhile, NZPA reported that 20 people were trapped on the 12th floor of the Forsyth Barr building, on Colombo Street.

One of those trapped, Gary Moore, said he and 19 other colleagues were stuck on the 12th floor because the stairwell had collapsed.

People were in a state of shock but were not injured, he told NZPA.

Shallow quake

GNS Science said today's quake was centred at Lyttelton at a depth of 5km at 12.51pm.

GNS said the earthquake would have caused more damage than the original 7.1 earthquake on September 4 because of its shallow depth.

Its data centre manager Kevin Fenaughty said residents said the quake's epicentre was located in the "worst possible location" for the city.

"It's a nightmare. A lot of people were just getting back on their feet after the original quake."

Another earthquake of 4.5 struck at 1.21pm, 10 km east of Diamond Harbour.

Streets flooded

Herald reporter Jarrod Booker said the shake lasted approximately one minute and was extremely violent - rocking buildings back and forth.

He said people had left buildings and were out on the streets where tarmac had cracked and water mains had burst, causing extensive flooding.

Tuam Street had become a river as water poured from ruptures in the road and was impassable in places.

The whole central city was in grid lock as people tried to evacuate central businesses to check their homes, Jarrod Booker said.

Most traffic lights were out and cars were also having to negotiate around hordes of people on foot.

Jarrod Booker said that he could hear sirens but that it would be difficult for emergency services to access the city because of the gridlock.

"Even sitting in a car you can feel continual shaking on a smaller scale than the original quake," he said.

Some pedestrians were standing on the footpaths and staring into space, apparently in shock.

'Great confusion'

Mayor Bob Parker said he was "thrown quite a distance" by the earthquake.

"That was, in the city central anyway, as violent as the one that happened on the 4th of September," he told Radio New Zealand.

Mr Parker said there were scenes of "great confusion" on the streets, also saying the roads were jammed as vehicles sought to get out of the central city.

"I know of injuries in my building and there are unconfirmed reports of serious injuries in the city."

Mr Parker did not know the extent of damage to the city's infrastructure, but advised people not to drink the water supply.

"We've been through this before this once, we now need to think we did at that time."

Buildings collapsed

Jarrod Booker said Christchurch's historic cathedral of the Blessed Sacrament on Barbadoes Street had half collapsed, with the remaining part of the building filled with cracks.

There was huge damage to other older buildings with large amounts of debris falling to the ground, he said.

He said the carpark at the Christchurch Star had turned into a river with huge cracks and that the roads had risen in areas.

People were comforting people outside amid a general state of shock as they tried to absorb what had happened, he said.

Radio New Zealand reported widespread damage to the city centre, with a church on Durham St collapsed and concrete lifted by up to a metre.

TV3 reported the Provincial Chambers Building had collapsed and it was believed people were trapped inside.

A listener told Newstalk ZB that the Piko Wholefoods building on Kilmore Street near the city centre, which was hit in the September 4 earthquake, was now "practically non-existent".

The spire on the Christchurch Cathedral had also collapsed.

A Newstalk ZB reporter in Christchurch said liquefaction was spewing out of the ground at St Albans High School.

School children had to be removed from the fields with liquefaction also spewing from the tennis courts.

Civil Defence response

Speaking to media at the Beehive's National Crisis Centre, Director of Civil Defence John Hamilton said a response plan was now being put together using all available national resources.

"That includes extra fire people, extra police personnel, assets from the Defence Forces. International offers of assistance are coming through from Australia in particular."

Mr Hamilton said the earthquake was a level three crisis - the highest for a localised event.

Phone lines are down and calls are not being connected to emergency services. Telecom said it is working to understand which services have been affected by the earthquake and get these restored as soon as possible.

Flights into Christchurch have been put on hold while Christchurch Airport checks the state of its runway. So far, four international flights have been diverted to Wellington Airport.

Today's quake was shallower and closer to Christchurch than the original Darfield quake, which took place 30km west of the city at a depth of 33kms.

Civil Defence advice

The Civil Defence has issued the following advisory:

Check yourself first for injuries and get first aid if necessary before helping injured or trapped persons.

Assess your home or workplace for damage. If the building appears unsafe get everyone out. Use the stairs, not an elevator and when outside, watch out for fallen power lines or broken gas lines. Stay out of damaged areas.

Look for and extinguish small fires if it is safe to do so. Fire is a significant hazard following earthquakes.

Listen to the radio for updated emergency information and instructions.

Do not overload phone lines with non-emergency calls.

Help people who require special assistance - infants, elderly people, those without transportation, families who may need additional help, people with disabilities, and the people who care for them.

Detailed safety advice will come from local authorities and emergency services in the area. People should act on it promptly. MCDEM, local civil defence authorities and scientific advisors are closely monitoring the situation.

How this footy club reduced injuries in 2020 season

Premium Content How this footy club reduced injuries in 2020 season

THE team got some extra help from Southern Cross University to ensure their players...

Fatal shooting of inmate to be investigated

Premium Content Fatal shooting of inmate to be investigated

The coroner has raised questions about the evidence heard

Ballina man stole from locals to fund lawnmowing business

Premium Content Ballina man stole from locals to fund lawnmowing business

He was concerned about his reputation, not his victims, judge said