The shallow tremor hit some 90 kilometres north of the South Island city of Christchurch which was devastated five years ago by a 6.3 tremor which killed 185 people in one of New Zealand's deadliest disasters.
Monday's quake, initially put at 7.4 but later upgraded, struck at 12.02am (6.02pm Thailand time on Sunday). It was only 10 kilometres deep and felt throughout most of the country.
The main tremor was followed by a series of strong aftershocks and there were reports of damaged buildings in the small rural township of Cheviot near the epicentre.
"It was massive and really long," Tamsin Edensor, a mother of two in Christchurch, told AFP, describing the powerful quake as the biggest since the deadly 2011 tremor.
"We were asleep and woken to the house shaking, it kept going and going and felt like it was going to build up."
In a brief message the Prime Minister John Key tweeted: "I hope everyone is safe after the earthquake tonight."
The ambulance service said it did not receive any reports of quake-related injuries.