Buildings have been evacuated and at least two people rescued from a collapsed church as Christchurch was rocked by two aftershocks, the largest measuring magnitude-5.5.
Police said St John's Church in central Christchurch had collapsed, trapping two people, who had been rescued.
Meanwhile, news website stuff.co.nz reported that people were feared trapped in a collapsed building on the corner of Stanmore and Worcester streets, according to police.
The biggest tremor hit about 1pm (1100 AEST) and was centred 10km southeast of Christchurch at a depth of 11km.
The second quake - which measured 4.4 - was centred in the same place and at the same depth.
Buildings evacuated included Canterbury University, a shopping mall and a supermarket in Wainoni.
There have been reports of liquefaction bubbling up from the ground in the central Christchurch suburb of Richmond and the outer suburbs, the NZ Herald reported.
There have also been reports of power loss and downed phone lines around Christchurch.
http://news.ninemsn.com.au/world/8260517/two-rescued-as-quake-rattles-christchurch