The Nisshin Maru cut short its whaling and sped north of the Ross Sea with two Sea Shepherd ships on its tail on Monday, its hunt disrupted only days after arriving in the whaling grounds.

Rare, graphic images of minkes being butchered on the deck of the factory ship were captured by the activists in a helicopter inside the International Whaling Commission's Southern Ocean whale sanctuary.

''It's just a gruesome, bloody, mediaeval scene which has got no place in this modern world,'' said Sea Shepherd Australia chairman Bob Brown.

The engagement marked the resumption of hostilities between the two sides for a 10th season, as a decision on the legality of the hunt is awaited from the International Court of Justice.

A third Sea Shepherd ship, the Bob Barker, was headed for Tasmania's Macquarie Island in an attempt to shake off a pursuing Japanese ship, with all whaling vessels banned from Australian waters.

This foreshadowed a test of the Abbott government's resolve against whaling, which Dr Brown questioned after Environment Minister Greg Hunt failed to deliver on an election promise to send a customs ship to monitor the kill. Mr Hunt reconfirmed a government commitment to flights by the Australian Customs and Border Protection Service, which he said was the first monitoring effort in six years. ''It will also allow us to monitor multiple ships in a diversely spread fleet,'' Mr Hunt said.

But with the conflict currently in New Zealand's search and rescue zone, the spotlight is turning on an angry demand of Sea Shepherd by its Foreign Minister, Murray McCully.

Mr McCully said in a letter to Sea Shepherd Australia's managing director Jeff Hansen that he was ''very disappointed'' with the group over its ''unacceptable'' previous non-compliance with New Zealand government directives. He demanded the group's three ships report their positions twice daily while in the NZ search and rescue zone.

Dr Brown said Sea Shepherd may comply if given a public guarantee the same requirement was being fulfilled by the Japanese fleet.

Japan's consul-general in Melbourne, Hidenobu Sobashima, said the government would not comment on statements by Sea Shepherd, but stood by its belief that the whaling was lawful research for scientific purposes.

Mr Sobashima said unlawful violent activities by Sea Shepherd were unacceptable. ''The government of Japan has repeatedly requested the government of Australia … to take effective measures to ensure the safety of navigation at sea,'' he said.