A massive earthquake with a magnitude of 7.8 rocked the island nation of Tonga, triggering a panic evacuation in a New Zealand town after tsunami warnings were briefly issued for the South Pacific.

Map locating the 7.8 magnitude earthquake which has struck Tonga[AFP]

Although the warnings were withdrawn within two hours, hundreds of people in the New Zealand coastal town of Gisborne, more than 2,200 kilometres (1,375 miles) from the quake's epicentre, fled their homes.

"Most of the coastal communities in Gisborne evacuated," regional civil defence controller Richard Steele told national radio.

"Things got a bit out of control."

But while there was panic in New Zealand, the 110,000 residents of Tonga were unaware a tsunami warning had been issued.

"Due to a breakdown in an internal communications' system, the Tonga authorities received no warning at all. Also, there seemed to be no internal mechanism for warning," said Kevin Vang of the Australian-Pacific Centre for Emergency and Disaster Information.

The US Geological Survey (USGS) said a "great" quake, initially measured at magnitude 8.0, struck at 4:26 am (1526 GMT Wednesday) in the middle of the islands that make up Tonga.

The epicentre was recorded 160 kilometers (100 miles) northeast of Tonga's main island of Nuku'Alofa and 16 kilometers below the Earth's surface, a relatively shallow distance which increases the likelihood of a tsunami.

It was the largest earthquake recorded by the USGS since a 8.6 temblor off the Indonesian island of Sumatra in March 2005, and immediately sparked fears of a repeat of the 9.0 Asian tsunami which killed 220,000 people in December 2004.

But despite the ferocity of the quake and aftershocks of magnitude 5.4 and 5.1, there were few reports of injury or damage in Tonga.

One hotel guest, identified as South Korean national Song Sang Hoon, hurt his leg when he jumped from a third-floor window.

"He was the only tourist injured. He jumped from his room, maybe he was afraid," said William Vea, the night receptionist at the Pacific Royale Hotel.

Once they assessed the damage was minimal, mainly broken glass and stock tipped from shop shelves, Tongans went back to bed. But in Gisborne, on New Zealand's east coast, residents packed what they could in the middle of the night and headed for higher ground.

Russell Beazley, a worker at a 24-hour petrol station, said it was inundated with people stocking up before heading out of town.

"It was pretty scary stuff looking at all the locals come in, and they were all frightened and grabbing all the supplies they could get," he said.

Kelly Cullen said she and her husband drove their children towards the nearest hill but, hearing it was too crowded, they kept driving. "I'm actually due to have a baby so we thought we better be organised," she said.

The flight from Gisborne sparked a row over how residents were misled.

Many blamed authorities for not correcting news reports when they knew there was no tsunami, but Civil Defence Minister Rick Barker blamed the BBC and other media.

"If the BBC, which is a reliable news outlet... says there is a tsunami heading to New Zealand, which it wasn't, and said it was aimed at Gisborne, which it wasn't, and said that there was a police alert, which there was not, and people accept the value of that news report, then the BBC is at fault," he said.

New Zealand's Geological and Nuclear Sciences department said the earthquake was felt in much of the North Island of New Zealand.

Tsunami Warning Center initially called on New Zealand and Fiji to take immediate action against a possible giant wave, but New Zealand civil defence officials said it was evident within 30 minutes there would be no significant tsunami.

In Fiji police advised residents of villages in low-lying areas to move to higher ground, while tourists in resorts were told to stay on higher floors where possible.