A large earthquake in Wellington early this morning shook locals out of bed but there were no immediate reports of damage.
The tremor, measuring 5.2 in magnitude, hit at 2.10am, GNS Science reported.
It was centred 20km south of Wellington and was 30km deep.
It was followed by a 4.3 aftershock at 3.52am.
Police were inundated by 111 calls from people wanting more information on the quake but had no reports of damage, a central police communications spokesman said.
GNS Science duty seismologist Ken Gledhill said the first earthquake was felt from the Kapiti Coast to the top of the South Island.
More than 100 reports of shaking were received by the GeoNet website within 25 minutes of the earthquake.
The GeoNet website crashed briefly from heavy traffic following the quake.