A powerful earthquake has struck the southern New Zealand city of Christchurch collapsing buildings, burying vehicles under debris and sending rescuers scrambling to help trapped people amid reports of multiple deaths.
The 6.3-magnitude quake struck the country's second-largest city on a busy weekday afternoon.
Christchurch Mayor Bob Parker declared a state of emergency and ordered people to evacuate the city centre.
"Make no mistake this is going to be a very black day for this shaken city," he said.
Victims were said to have been among two buses that were struck by falling buildings, while emergency workers were moving to rescue survivors trapped in partially collapsed buildings in locations around the country's second largest city.
The multistory Pyne Gould Guinness Building, housing more than 200 workers, has collapsed and an unknown number of people are trapped inside. Television pictures showed rescuers, many of them office workers, dragging severely injured people from the rubble.
New Zealand's TV3 said 24 people were trapped on the 17th floor of the 19-story Forsyth Barr office building, near the cathedral. The building was intact but a stairwell had collapsed, it said.
The city's emblematic cathedral was one of the buildings that took significant damage, while cars were buried under rubble and roads buckled as the tremor opened fissures in the ground.
"It is huge. We just don't know if there are people under this rubble," a priest standing outside the rubble of a damaged cathedral told New Zealand television.
All airports and airspace in the country were shut down and all flights into, out of and around the country were put on hold immediately after the earthquake.
Airways NZ, New Zealand's national Air Traffic Control organisation, is based in Christchurch.
Local TV showed bodies being pulled out of rubble strewn around the city centre, though it was unclear whether any of them were alive.
It was the second time in five months the city has been struck by a major earthquake. The epicentre of last September's earthquake was 30 miles west of Christchurch. About 100 people were treated at hospital with earthquake-related injuries on that occasion.
Power and water was cut and hundreds of dazed, screaming and crying residents wandered through the streets as sirens blared throughout Christchurch in the aftermath of the quake, which was centred three miles from the city.
The US Geological Survey said the tremor occurred at a depth of 2.5 miles. Christchurch has been hit by hundreds of aftershocks since a 7.1 magnitude earthquake struck on 4 September last year, causing extensive damage and a handful of injuries, but no deaths. New Zealand, which sits between the Pacific and Indo-Australian plates, records on average more than 14,000 earthquakes a year, of which about 20 would normally top magnitude 5.0.
Christchurch is home to about 350,000 people and is considered a tourist centre and gateway to the South Island.