Hundreds of Antarctic icebergs are drifting north toward New Zealand, prompting a warning to all ships in the area.

The nearest, about 90ft tall, was 160 miles south-east of Stewart Island and was part of a flotilla that could be seen on satellite images.

The alert comes three years after cold weather and favourable ocean currents saw dozens of icebergs float close to New Zealand's southern shores for the first time in 75 years.

No major shipping lanes or substantial fishing grounds are in the area, but most ships there have little hull protection if they collide with an iceberg — which typically has 90% of its mass under water.

Rodney Russ, expedition leader on the tourist ship Spirit of Enderby, spotted a 500ft-long iceberg about 60 miles north-east of Macquarie Island and heading north — about 500 miles south of New Zealand. Australian scientists reported another mass of 20 icebergs drifting north past Macquarie Island two weeks ago.

Satellite images showed the group of icebergs, spread over a sea area of 600 miles by 440 miles, moving on ocean currents away from Antarctica. One of the images alone had 130 icebergs and another had 100.