New Zealand earthquake: Dozens dead, hundreds trapped as Christchurch is torn apart

• Rescue teams try to get into a collapsed building in central Christchurch. Picture: Getty Images

The quake, measuring 6.3 on the Richter Scale, struck Christchurch at the height of the working day causing widespread destruction and injury.

A state of emergency has been called in the city on New Zealand's South Island as rescue teams try to recover people still trapped under rubble and debris.

Eyewitnesses said the three-mile (5km) deep tremor, believed to be an aftershock from a 7.1 magnitude earthquake which struck last September, levelled high-rise buildings, tore up pavements and sprayed rubble onto the streets below.

Prime minister John Key held an emergency Cabinet meeting then rushed to the stricken city.

"It is a just a scene of utter devastation," he said, before revealing the death toll was 65, and may rise.

"This may be New Zealand's darkest day."

Earlier he had said the disaster had struck at a time when the city was at its most populated, with people at work and children at school.

• A man runs for cover in the aftermath of the Christchurch earthquake. Picture: Getty Images

Mr Key said people were being told to get out of the city for their safety, while the airport was closed and Christchurch Hospital was evacuated.

New Zealand police said in a statement that there were reports that two buses had been crushed by falling buildings.

• British Nationals affected by the quake are asked to contact the Global Response Centre on 0044 20 7008 1500.

• Do you know anyone caught up by events in Christchurch? Click here to get in touch with The Scotsman

• Tourists speak of devastation

• Christchurch earthquake: In pictures

British backpacker Christopher Ratcliffe, 27, was forced to shelter under a desk in Christchurch library when the quake struck.

"The building started to shake, my computer screen started to flicker and then the books started to fly off the shelves so I just dived under my desk," said the traveller from Sutton Coldfield, West Midlands.

"I have experienced a few aftershocks before this, but this was totally different.

"When I came outside the city looked like a bomb had hit it. There was dust and smoke in the air and bits of glass and rubble falling from the tops of buildings. People were walking around covered in blood and in tears - it was just shocking."

• An iconic Christchurch tram is covered in debris. Picture: Getty Images

Mr Ratcliffe, who has been in Christchurch for a month while on a round-the-world trip, continued: "As I walked through the city centre there was damage on every road and some roads were totally destroyed. Half of the front of the Cathedral had fallen off and there were ambulances and helicopters everywhere. It was just madness."

The British tourist said many of the injured were being treated at an emergency treatment centre in Christchurch's Latimer Square, with helicopters airlifting casualties from other parts of the devestated city.

Roads around the city centre had also been closed off while emergency workers co-ordinate the rescue operation, which is being hampered by flooding from burst water pipes.

Christchurch, home to about 350,000 people, is a major tourist centre for tourists to the popular South Island.

The Foreign Office said it was "urgently" seeking information about British casualties. It is not know if any Britons are among the dead.

A spokesman for the Foreign Office said: "We are in close touch with the local authorities an are urgently seeking information. The High Commission in Wellington have mobilised a consular response and stand ready to provide any consular assistance that is required."

The British High Commission in Wellington confirmed buildings had collapsed, water pipes had burst and the Cathedral in the centre of the city had sustained damaged.

Spokesman Chris Harrington said: "The tremor has been classified as an aftershock and although it was not as strong as the quake last September, there have been reports of serious injuries. Its centre was about 10km outside Christchurch and 5km deep.

"The quake hit during the middle of the day, whereas the September incident happened at 4am in the morning so it has done more damage."

• The force of the earthquake destroyed a city centre car park. Picture: Getty Images

Mr Harrington added that buildings which had survived the September quake had been demolished.

A September 4 earthquake wrecked hundreds of buildings in the city causing an estimated four billion New Zealand dollars of damage. A strong aftershock in December caused further damage to buildings.

The city was still rebuilding from those quakes when the latest one hit.

There were other reports of fires burning in the city and people being trapped in buildings.

New Zealand sits on the Pacific "ring of fire" - an arc of earthquake and volcanic zones stretching from Chile in South America through Alaska and down through the South Pacific.

It records more than 14,000 earthquakes a year - but only about 150 are felt by residents, and fewer than 10 a year do any damage.