Masonry and glass rained down near post-Christmas shoppers as a magnitude 4.9 earthquake rocked Christchurch on New Zealand's South Island on Sunday.

Safety fences are erected around fallen bricks on Madras Street in central Christchurch, New Zealand, on Sunday, after a series of aftershocks. (Simon Baker/New Zealand Herald/Associated Press)

No one was injured, but at least 20 buildings in the city's centre were damaged by the quake, which scientists said was the latest of hundreds of aftershocks since a 7.1 magnitude earthquake struck Christchurch on Sept. 4. That quake caused extensive damage and a handful of injuries, but no deaths.

Sunday's earthquake also came a few hours after a magnitude 7.3 earthquake struck under the sea near Vanuatu. There were no reports of damage or injuries from that quake, though it generated a small tsunami wave.

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.

Quake struck during Boxing Day sales

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 sidewalks, no one was hurt, according to police.

Large parts of the central business district were cordoned off after the quake and power was cut temporarily.

Monitoring agency GNS Science said the quake occurred at 10:30 a.m. within three miles (five kilometres) of Christchurch at a depth of eight miles (12 kilometres).

It was the largest of more than a dozen aftershocks that rattled Christchurch throughout Sunday. Scientists said the temblors were related to the September quake and could continue for some time.

Earlier on Sunday, 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 are felt by residents, and fewer than 10 a year do any damage.