Wellingtonians had a shaky night's sleep as two earthquakes rocked the city in the early hours of the morning. The quake, which measured 5.2 on the Richter scale, was centred 20 kilometres south of Wellington at a depth of 30 kilometres. It struck at 2.10am Friday.

Some residents say it is the biggest earthquake they have felt in 35 years. A second quake followed at 3.52am in the same area and measured 4.3.

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.

However some residents have reported cracks in ceilings. GNS Science duty seismologist Ken Gledhill says 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.