Warning as earthquake hits New Zealand's South Island

No-one was injured, but at least 20 buildings in the city's centre were damaged by the tremor, which scientists said was the latest of hundreds of aftershocks since a 7.1 magnitude earthquake struck Christchurch on 4 September.

That quake caused extensive damage and a handful of injuries, but no fatalities.

Yesterday's quake also came a few hours after a magnitude 7.3 earthquake struck under the sea near Vanuatu.

The quake struck just after midnight about 140 miles south of Vanuatu's capital, Port Vila.

The US Geological Survey said it was about 15 miles below the ocean floor.

A small tsunami wave was recorded on some coastlines at Vanuatu, the Pacific Tsunami Warning Centre said following the quake.

New Caledonia and Fiji also were warned a tsunami was possible on their coasts, but the warning was cancelled about an hour and a half after the New Zealand quake.

There were no other reports of damage or injuries.

New Zealand and Vanuatu are situated 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.

The quake struck Christchurch in the late morning as shoppers thronged central city streets to take advantage of traditional Boxing Day sales.

Although masonry and glass fell across footpaths, no-one was hurt, according to police.

Acting mayor Ngaire Button said last night that power cut off by the quake had been restored, and council staff and civil defence staff workers had been called back to work to get "all the information we can".Large parts of the central business district were cordoned off after the quake and power was cut temporarily.

Christchurch police commander, Inspector Derek Erasmus, told media that the cordons would remain in place until buildings could be assessed for possible damage from the quake.

He said: "We want to cause the least disruption possible so that activity in the city can return to normal."

"We need to maintain cordons in these locations because of the potential risk to safety from damaged buildings, including falling masonry and brickwork, and damaged windows," he added.

"These cordons will be assessed again tomorrow and we hope that we can further reduce the extent of the road closures."

Monitoring agency GNS Science said the quake occurred at 10:30am within three miles of Christchurch at a depth of eight miles.

It was the largest of more than a dozen aftershocks that rattled Christchurch throughout yesterday.

Scientists said the tremblers were related to the September quake and could continue for some time.

Earlier yesterday, a 5.9 magnitude quake was felt across New Zealand's North Island, but no damage or injuries were reported.

The quake was centred north of volcanic White Island off New Zealand's east coast.

New Zealand sits above an area where two tectonic plates collide.

The country records more than 14,000 earthquakes a year, but only about 150 of those are felt by residents, and fewer than ten earthquakes a year do any damage.