A series of powerful earthquakes, including one of magnitude 6.0, rocked New Zealand's stricken city of Christchurch on Monday causing further damage.
More buildings came down and there was severe disruption to electricity and water supplies, with Christchurch still recovering from the destruction of the deadly 6.3 earthquake in February which killed 181 people.
"We are in a serious situation," said Bob Parker, mayor of New Zealand's second-largest city.
The National Crisis Management Centre controller David Coetzee said there were no reported fatalities from the latest tremors but at least 10 people were injured and more buildings in the central business district collapsed.
Power company Orion said electricity had been cut to 54,000 homes and council staff said they had lost water pressure across the city.
The US Geological Survey measured the largest quake at a magnitude of 6.0, with a depth of nine kilometres and the epicentre some 14 kilometres from the heart of the city. It hit at 0220 GMT.
It followed a string of shocks early Monday, including a 5.2-magnitude jolt which caused building damage in the city, and came just as schools were about to end for the day. All schools have now been closed until further notice.