New Zealand Prime Minister John Key has declared a national state of emergency as the death toll from Tuesday's earthquake in Christchurch rose to 75. There are now 55 bodies in a morgue and another 20 being transported there following the 6.3-magnitude tremor. Police have said there is "incredible carnage right throughout the city", with "bodies littering the streets". More than 300 people are still missing. Forty-eight were pulled out from collapsed buildings alive overnight.

Christchurch Hospital is bracing for a sudden increase in new babies as women go into premature labour as a result of the quake. The number of babies being born spiked following the September 4 quake and a repeat is likely today.

Prime Minister John Key is on ONE News. He says 65 people are confirmed dead. He warns the death toll may rise.

Geonet reports that another three aftershocks have occurred in the last 40 minutes. A magnitude 4.6 quake was measured 10km east of Lyttelton at 3.38pm. That was followed by another five minutes later, a 4.5 quake 10km south-west of Christchurch. The third took place at 4.04pm and measured 4.6 on the Richter scale. It was centred within 5 km of Christchurch and took the total to 10 aftershocks since the 6.3 earthquake at 12.51pm.

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. The Sept. 4 quake wrecked hundreds of buildings in the city, and caused an estimated $3 billion in damage. A strong aftershock in December caused further damage to buildings. The city was still rebuilding from those quakes when Tuesday's temblor hit.

Police are arresting people who are getting in the way of emergency services trying to help those trapped and injured.

Civil Defence Minister John Carter said all the South Island hospitals apart from Invercargill had been emptied to make way for earthquake victims. Mr Carter and preparations had been made for a state of emergency to be declared. He said the number of fatalities and the extent of the damage was still unclear.

The city has run out of ambulances, and private vehicles are being used to ferry the injured to triage centres. The city's main hospital has been evacuated.

Local police said there were reports of multiple fatalities, including that two buses had been crushed by falling debris. There were also reports of fires and of people being trapped in collapsed buildings, they added.

There are reports 60 percent of Lyttelton has been virtually demolished.

A powerful earthquake hit the New Zealand city of Christchurch on Tuesday, collapsing buildings, burying vehicles under debris and sending rescuers scrambling to help trapped people amid reports of multiple deaths.