The quake, first reported as 6.3 magnitude but later downgraded to 5.6, was centred about 200 kilometres northeast of the capital Wellington, according to the US Geological Survey. It was at a relatively shallow depth of 10 kilometres.
The Pacific Tsunami Warning Center did not issue a tsunami warning.
New Zealand was last week hit with a powerful magnitude 7.8 quake near the coastal South Island town of Kaikoura that killed two people.
