Japanese factory ship
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Campaign group pursues Japanese whaling fleet

6 January 2014 Last updated at 14:54 GMT

Australian anti-whaling activists say they are pursuing a fleet of Japanese ships they say are involved in the killing of four whales in the Southern Ocean.

The campaign group says the whales were killed within an internationally recognised whale sanctuary.

Japan says its whaling expedition was for scientific research.

Jon Donnison reports from Sydney.