Nearly 450 Australians attending a medical conference have been caught up in the Christchurch earthquake.
Doctors and nurses from across the country were at the annual meeting of the Urological Society of Australia and New Zealand when Christchurch was rocked.
There were 600 delegates registered for the meeting; 430 were Australians of which 160 were Victorians.
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Event Planners' human resources director Suzanne Best said the convention centre had been evacuated and all the delegates were believed to be safe.
The convention began yesterday and was due to finish on Thursday.
The centre is located in the heart of the CBD, a few streets from Christchurch Cathedral.
A doctor from St Vincent's Hospital, Marni Basto, was filmed by the ABC in front of Christchurch Cathedral.
She was on hand to help any survivors who might have been in the cathedral, which partly crumbled in the 6.3 magnitude earthquake.
"We're just waiting for them to clear ... any structural damage that would put us at harm and, once we get that OK, we'll head in and try and help some people," Dr Basto was reported on radio 3AW as saying.
"We're just trying to accumulate any supplies that we can; we've taken some from the stores around and everyone's been very helpful giving medical supplies, everything that they've got so far."
Nathan, a Melbourne surgeon at the convention, said he had seen major destruction around the city following the quake, which was followed five to 10 minutes later by a strong aftershock.
He feared there would be fatalities, including at the cathedral in the main square where the steeple had been destroyed.
"I'm over here at a convention in Christchurch and just in the middle of a session, you know, the speaker was speaking and suddenly the ground shook, and glass was breaking and it was really quite frightening," Nathan told radio 3AW.
"Fortunately nobody from our convention appears to be severely hurt but there's a lot of major destruction here in Christchurch.
"I don't know if you know the church in the centre of town, the steeple has fallen over. I'm certainly fearful that there will be some fatalities among that, and a lot of the buildings just adjacent to the city square, the awnings of buildings have all fallen down and a lot of buildings around here, it looks pretty shaken up. All the water mains have burst. There's water seeping up through the roads. It's a fairly scary place to be right now.
"The road has been buckled up, just like looking at bits of liquorice sort of burst up on the seam. It really is quite incredible."
He said buildings had fallen on to cars, while "lots of second storeys have fallen on to first storeys".
"I guess a lot of us now don't know what to do. Some of us were thinking to go down the hospital to help out but we were told not to leave the area because it's not safe," Nathan said.
Among the Victorian delegates were members of the Victorian Urological Nurses Society.
Australia's women's cricket team, the Southern Stars, were training indoors in the township of Lincoln, about 25km from Christchurch, when the quake hit.
Head coach Richard McInnes said the team's 14 players and five staff were safe.
"(We) just heard the noise like two massive big roller doors opening and then the floor started to move, which is a big concrete slab ... and the whole floor moved like a surfboard," he said.
The team have been unable to return to Christchurch were they were due to play a match on Thursday and are staying in residential halls at Lincoln University.
- with Alana Rosenbaum
The Piko Wholefood building in Christchurch was badly damaged by the earthquake. 
A magnitude 6.3 earthquake struck the  of New Zealand at 12:51 PM local time on Tuesday (Monday 23:51 UTC). At least 75 people have been killed by collapsing buildings in central , with more feared. Mayor  said 55 bodies had been identified and there were a further 20 unidentified bodies. The spire of the iconic Anglican  has fallen and rubble is strewn throughout the central business district. Roads and carparks have cracked and lifted, and two buses are reported to be crushed under the bus exchange. Pools of mud have erupted due to burst water mains and liquefaction.  Boulders and falling cliff faces have destroyed buildings on hillside suburbs.  Fears for the safety of nearby towns Lyttelton and Akaroa are exacerbated due to communication problems.

The earthquake was centred near , at a depth of five kilometres, according to the . Unlike previous quakes in the region that caused no fatalities, Tuesday quake was shallower and closer to the central city and the damage was much worse. Condemned buildings, weakened by last year's widespread earthquakes, were destroyed. Some aftershocks have occurred in the area after the earthquake. The largest so far was a magnitude 5.6 which occurred at 7:04 p.m. February 21  (1:04:18 p.m. local time, February 22). 

Mayor Bob Parker has stated that as many as 25 major buildings in the city are destroyed. Urban Search and Rescue efforts are focussed on people trapped in the remains of Canterbury Television and Pyne Gould Corporation office buildings. The historic  in Christchurch has half collapsed, while the old Canterbury Provincial Chambers building, Piko Wholefoods, and a church on Durham Street have been destroyed.

The earthquake also caused an estimated 30 million tons of ice to break off of the Tasman Glacier forming icebergs in a lake near its foot. Tourists on boats at the time of the quake say waves of 3.5 meters swept the lake for at least 30 minutes following the event. The glacier sits on the country's west coast, approximately 120 miles (200km) from Christchurch. No injuries were reported.

Many people are trapped in damaged buildings or under rubble, but emergency services have been hampered by gridlock as motorists and pedestrians evacuated the CBD. The main hospital remains operational despite one damaged ward being closed, and three triage centres have been set up to provide medical aid. Several hundred delegates attending a medical conference in the city, the great majority from Australia, have been trapped in the city; some of these are assisting with tending to the injured.

Electricity, telephone services, and traffic lights suffered widespread outages. Orion and Telecom are attempting to assess the damage, and generators have been sent down from Auckland to replace the backup generators in the city. Civil Defence is mounting a response with all available national resources, and Cabinet is holding an emergency session. Speaking to ,   said he was "thrown quite a distance", that there were scenes of "great confusion" on the streets, and that the quake was "as violent as the one that happened on the 4th of September". The emergency telephone code, 111 was not working for the entire region of  but is apparently stable as of approx. 4 pm . Christchurch Airport is currently closed to all but emergency flights. Speaking after the earthquake, Bob Parker said at least 200 people are believed trapped under rubble, saying that New Zealand are "going to be presented with statistics that are going to be bleak".