A series of strong earthquakes has hit New Zealand, sending people scrambling for cover and causing the capital, Wellington, to shake "like jelly".
The first tremor, a 6.5-magnitude, struck at 2:31pm local time in the Cook Strait, around 58 miles (94 km) west of Wellington at a depth of six miles (10 km), the US Geological Survey said.
It was followed by several aftershocks measuring up to 5.7 and was felt from Christchurch in the South Island to Auckland in the North Island.
Authorities said there were no initial reports of injuries or major damage to buildings, and no tsunami warnings have been issued.
The quake caused a violent jolt in Wellington.
"Lots of aftershocks. 'Beehive' wobbling around like a jelly, but all OK," economic development minister Steven Joyce tweeted, referring to New Zealand's distinctive parliament building.
Resident Juli Ryan tweeted: "That was pretty wild, I was sitting in my parked car watching buildings shake like leaves."
There were reports of power cuts to areas of the South Island, and Wellington's airport was briefly closed to check the runway for damage.
Train services were also stopped in case railway tracks had buckled in the quake, but there were no reports of significant damage.
Lifts were out of action in some office buildings and, as the aftershocks continued, many businesses sent their workers home early, causing large traffic jams in the capital.
A quake of a similar strength in the same area three weeks ago broke water mains, smashed windows and downed power lines.
New Zealand is part of the so-called Pacific 'Ring of Fire' that has regular seismic activity - around 5,000 tremors a year.
A massive earthquake in the city of Christchurch in 2011 killed 185 people and destroyed much of the city's downtown.