A series of strong aftershocks from a September earthquake has rattled Christchurch in New Zealand on one of the busiest shopping days of the year.
The most powerful tremor was 4.9 magnitude and its impact was magnified by its proximity to the city centre.
Buildings were damaged, power supplies temporarily cut and a large shopping centre was evacuated.
The city of 370,000 people was hit by a 7.1-magnitude earthquake three months ago, causing widespread destruction.
Two people were seriously injured in that quake, and older buildings including some landmarks were destroyed.
Scientists say the tremors which continue to shake the area are related to the September quake and warn they could continue for some time.
On Saturday, a 7.3 magnitude quake struck under the sea off Vanuatu, but there were no reports of damage or injuries.
Correspondents say it was a remarkable stroke of luck that no-one was hurt in Sunday's tremor.
It struck at 1030 (2130 Saturday GMT) within 5km (three miles) of Christchurch at a depth of 12km, said GNS Science monitoring agency.
Shop fronts were shattered and in some places masonry could be seen littering the streets.
Large parts of the central business district were cordoned off as police assessed damage to buildings.
"To witness that first hand, it really scared the living daylights out of me," one witness told reporters. "Buildings were exploding, and I thought it was glass but it was rock!"
One resident, Roger Cleave, who owns a music shop, said the latest shocks did more damage than September's quake.
"When we had the [earthquake in September] we had very little damage to stock. I think only one guitar fell off the wall and a couple of other items fell over. But this one was a lot more violent and a lot more stuff has fallen off."
A Civil Defence Emergency Operations Centre, to co-ordinate the response of emergency services, has been set up.