More than 100, and possibly hundreds, of Antarctic icebergs are floating towards New Zealand in a rare event which has prompted a shipping warning, officials said on Monday.

An Australian Antarctic Division glaciologist said the ice chunks, spotted by satellite photography, had passed the Auckland Islands and were heading towards the main South Island, about 450 kilometres (280 miles) northeast.

Scientist Neal Young said more than 100 icebergs -- some measuring more than 200 metres (650 feet) across -- were seen in just one cluster, indicating there could be hundreds more.

He said they were the remains of a massive ice floe which split from the Antarctic as sea and air temperatures rise due to global warming.

"All of these have come from a larger one that was probably 30 square kilometres (11.6 square miles) in size when it left Antarctica," Young told AFP.

"It's done a long circuit around Antarctica and now the bigger parts of it are breaking up and producing smaller ones."

He said large numbers of icebergs had not floated this close to New Zealand since 2006, when a number came within 25 kilometres of the coastline -- the first such sighting since 1931.

"They're following the same tracks now up towards New Zealand. Whether they make it up to the South Island or not is difficult to tell," Young said.

New Zealand has already issued coastal navigation warnings for the area in the Southern Ocean where the icebergs have been seen.

"It's really just a general warning for shipping in that area to be on the alert for icebergs," said Maritime New Zealand spokesman Ross Henderson.

The icebergs are smaller remnants of the giant chunks seen off Australia's Macquarie Island this month, including one estimated at two kilometres (1.2 miles) and another twice the size of Beijing's "Bird's Nest" Olympic Stadium.

Young earlier told AFP he expected to see more icebergs in the area if the Earth's temperature continues to increase.

"If the current trends in global warming were to continue I would anticipate seeing more icebergs and the large ice shelves breaking up," he said.

When icebergs last neared New Zealand in 2006, a sheep was helicoptered out to be shorn on one of the floes in a publicity stunt by the country's wool industry.