Scientists have reported a giant iceberg over twice the size of Sydney Harbor is on a slow but steady collision course with Australia.

A huge iceberg was identified near an island between Antarctica and Australia, an usual display in northern waters, Australian scientists announced on Thursday.

An iceberg has been spotted from the New Zealand shore for the first time in 75 years, one of about 100 that have been drifting south of the country.

After five years of being the world's largest free-floating object, the B-15A iceberg has broken into smaller pieces off Antarctica's Cape Adare.

The mammoth B-15A iceberg appears poised to strike another floating Antarctic ice feature, a month on from a passing blow that broke off the end of the Drygalski ice tongue. As this Envisat image reveals, this time its target is the ice tongue of the Aviator Glacier.