A magnitude 6.8 earthquake has struck south of New Zealand's capital Wellington, sending panicked workers and residents into the streets just weeks after a similar tremor struck the city.

Key points: Magnitude 6.8 quake struck at 12:31pm (AEST)

Magnitude 6.8 quake struck at 12:31pm (AEST) Quake hit 10km south-east of Seddon at a depth of eight km

Quake hit 10km south-east of Seddon at a depth of eight km Several aftershocks have been felt within a 30km radius of the original tremor

Several aftershocks have been felt within a 30km radius of the original tremor No tsunami threat has been issued

No tsunami threat has been issued No reports of fatalities

The quake hit 10 kilometres south-east of the town of Seddon at a depth of eight kilometres on Friday and has been followed by several aftershocks measuring more than magnitude 4.4.

So far, there have been no reports of fatalities and only superficial damage to buildings, though fire authorities said it was too early to assess the full impact.

There was no specific threat of a widespread tsunami, according to the Pacific Tsunami Warning Centre.

6.2 earthquake hit central New Zealand about an hour ago. University and business district evacuated again... — Juan Fdez Castellano (@juanfc21) August 16, 2013

Local reports said the quake was felt as far away as Gisborne, Auckland and Hamilton.

There were also reports of power cuts to areas of the South Island, and Wellington's airport was briefly closed to check the runway for damage.

Wellington's airport was briefly closed to check the runway for damage ( Google Earth )

Train services were also temporarily stopped in case rails had buckled in the quake, but police said they had received no reports of significant damage.

Vernon Small, Fairfax New Zealand’s National Affairs Editor Fairfax was in parliament when the quake struck.

"It was pretty scary. This was the strongest I'd felt," Mr Small told Radio Australia's Pacific Beat.

"There are a few broken windows and the trains are out, so there's a bit of congestion on the streets and a few people ran outside screaming.

"A few people [were] trapped in lifts that have been cleared but we seem to have escaped relatively unharmed.

"There is a report of a house collapsing in Seddon which is a small town very close to the epicentre on the South Island but we haven't got the details through yet."

That was the biggest earthquake I haveever felt. Amazingly nothing fell off shelves here. — Pat McCarthy (@DrPatMcCarthy) August 16, 2013

Lifts were out of action in some office buildings and, as the aftershocks continued, many businesses sent their workers home early on Friday afternoon, causing large traffic jams in the capital.

Bill Fry, who's a seismologist with GNS, in Wellington, says the quake was is similar to a 6.4 tremor which struck in the same area on July 21.

"We had a couple of relative large high sevens earthquakes before that and then we had 6.5s two weeks ago and then this look like a continuation of that sequence," he said.

There have been hundreds of aftershocks since the July quake, with residents fearing a repeat of a devastating quake that hit Christchurch in February 2011, killing 185 people.

Traffic jams in Welly, everyone trying to get out. — Darien Fenton (@DarienFenton) August 16, 2013

Wellington lies near five seismic faultlines and was the scene of the country's most powerful earthquake in 1855.

That devastating 8.2-magnitude quake caused four deaths and changed the city's entire geography, pushing the shoreline out 200 metres as it thrust the harbour floor upwards.

Anna Kaiser, a seismologist with the official GNS monitoring service, said it was impossible to predict how long the latest burst of activity would last.

"Certainly we expect aftershocks following an event like this," she said. "Unfortunately when we have something like this there's also an elevated chance of getting another earthquake of a similar magnitude."

New Zealand is on the boundary of the Australian and Pacific tectonic plates, forming part of the so-called "Ring of Fire", and experiences up to 15,000 tremors a year.

ABC/wires