WORKERS have fled New Zealand's capital, Wellington, after a severe earthquake measuring a magnitude of 6.6 rocked the nation.

New Zealanders huddled under desks as strong tremors struck the country -- as far north as Auckland and as far south as Dunedin -- at around 2:31pm local time.

There were a number of injuries from broken glass but no serious casualties have been reported.

Earthquakes damaged houses and there were reports of a home almost totally collapsing in Marlborough on the South Island.

Many buildings were evacuated and workers told to go home to allow structural assessments to be carried out. Lengthy traffic queues formed outside the city.

Emergency services rescued several people in Wellington trapped in lifts which stopped operating when the quake struck.

A number of aftershocks, measuring up to 5.7 in magnitude, have also been recorded.

Cabinet Minister Steven Joyce tweeted: "Lots of aftershocks. Beehive (parliament) wobbling around like a jelly, but all ok''.

There have been reports of power lines down in the Seddon area and police were advising caution on State Highway 1 south of Blenheim after large boulders had come down on the road.

It advised people not to drive unless absolutely necessary and to expect delays.

Wellington Free Ambulance said it had a spike in the number of calls it received but was unable to confirm any injuries.

Telephone networks were congested and Telecom advised people to send text messages rather than call.

Office workers in the city flooded onto the streets in the aftermath and there was broken glass in the central business district. Many buildings were evacuated and workers told to go home.

Wellington City Council advised residents to avoid driving home, as many of the capital's roads are in gridlock and some emergency service vehicles had trouble getting to callouts.

The council has not received any reports of major damage, a spokesman said.

About 2500 customers in the Wellington region lost power after the earthquake, Drew Douglas, a spokesman for Wellington Electricity said.

By 3.30pm 600 customers were without power, in Wrights Hill, Wainuiomata and Makara.

"We had a large number of homes out in Karori but it is back on now," he said.

"The company is working to restore power to the affected areas."

The New Zealand Stock Exchange temporarily ceased trading.

Rail and bus services in the capital were suspended and there were reports of boulders and power lines coming down on major roads.

Wellington Airport's runway was inspected and cleared. Dozens of aftershocks continued to rattle the area with a number magnitude 5 or greater.

The shake comes after a 6.5 quake in the same region on July 21 which caused minor injuries to 25 people and damage to dozens of buildings

When the earthquake hit that bloody hard. And all I could think of was leaving class to go get my little sister. — Esther Folau - Tavai (@_estherfolau95) August 16, 2013

Worst place to be during earthquake update: trapped in Salient storeroom amongst overloaded shelves. #eqnz pic.twitter.com/l59b7GQqej — Giancarlo (@louderthoughts) August 16, 2013

Text from Mum: "We're Ok. Chat later as a bit chaotic right now. Trying to get out of town!" #NZ #earthquake — Claire Nelson (@clairenelson) August 16, 2013

Reaction from residents on Twitter indicated the quake was larger than the one that rocked the city last month.

Everyone was under the desk for that one #EQNZ — Kerry McBride (@Kerry_McBride) August 16, 2013

"That was a heart beating quake. Lots of people under their desks in the press gallery," NZ TV1 news reporter Jessica Mutch said on Twitter.

"That was easily the biggest quake i've felt," @mikeforbes tweeted. "VERY shakey. house felt like it was wobbling forever."

"Oh my. That was very strong," Marcus Figueroa tweeted. "My car was wiggling while driving, I thought one of my wheels was coming off! #eqnz"

Won't be able to respond to individual Qs. Will let you know what's happening as we hear. Buses running. No trains for at least 4-6 hours. — Metlink Wellington (@metlinkwgtn) August 16, 2013

About 2500 customers in the Wellington region lost power after the earthquake, a spokesman for Wellington Electricity said and 600 were without power at 3.30pm.

The Joint Australian Tsunami Warning Centre issued a statement at 12.42 EST saying there is no tsunami threat to the Australian mainland, islands or territories.

The Centre said an undersea earthquake of magnitude 7.0 occurred at 12:31 PM EST on Friday 16 August 2013 near Cook Strait.

Cook Strait is the body of water separating New Zealand's north and south islands.

The earthquake was 11km deep, according to preliminary data from GeoNet.

###