"It's a civilian issue. We don't see an Australian military role," Defence Minister Robert Hill told reporters in response to calls for a navy patrol boat to be sent to the self-proclaimed Australian whale sanctuary.

"However, we don't condone any form of violent activity on any side," he said.

Hill was speaking shortly before the Sea Shepherd Conservation Society, which has been hounding the whalers in its ship the Farley Mowat, issued a threat to the Japanese fleet of six ships.

"Sea Shepherd Conservation Society believes it is time to escalate the confrontation with the Japanese whaling fleet and bring an end to the illegal and ruthless slaughter of defenseless whales in the Antarctic Whale Sanctuary," the group said in a statement.

The statement, headed "Sea Shepherd intends to ram and disable pirate whalers", quotes the group's founder and captain of the Farley Mowat, Paul Watson, as saying he was "tired of politicians being apologists for these criminals".

"We sideswiped the whaling supply ship Oriental Bluebird yesterday (Monday) and we intend to disable any pirate whaling vessel we find. We intend to uphold the laws protecting whales. This nonsense must be ended."

Watson, a founder member of the environmental group Greenpeace, left the organisation in 1977 after disagreements over tactics and has taken a more aggressive approach with Sea Shepherd.

Greenpeace has two ships also harassing the Japanese whaling fleet in the Southern Ocean.

The International Whaling Commission imposed a moratorium on commercial whaling in 1986 but Japan has continued hunting for what it calls scientific research -- a claim rejected by critics.

Japan Tuesday demanded that the Netherlands stop the escalating conflict.

"We have asked the Netherlands to stop the pirate-like dangerous activities by Greenpeace, as their boat is registered in the Netherlands," said Hideki Moronuki, chief of the whaling section at Japan's Fisheries Agency.

"The latest collision was really dangerous although we were lucky no one was injured. If activists further escalate their violent action, ignoring the calls for restraint by all authorities, we have to think about taking tougher measures," he told AFP.

Greenpeace has distanced itself from any violent tactics in the anti-whaling protest, and blamed the Japanese for a collision on Sunday between its ship the Arctic Sunrise and the Japanese factory ship the Nisshin Maru.

Watson said, however, he had deliberately collided with the Oriental Bluebird after "ordering" it to leave the hunting grounds.

"When they refused, we backed up the message by slamming our starboard hull against their starboard hull.

"There was no damage apparent to either ship aside from a long scratch along the hull of the Oriental Bluebird caused by a device attached to the Farley Mowat's hull called the 'can opener'," he said.

The Japanese whaling authority, the Institute of Cetacean Research, has called on both Greenpeace and Sea Shepherd to "stop at once their dangerous and criminal actions."

The Arctic Sunrise and another Greenpeace ship Esperanza have been shadowing the Japanese fleet since December 21, attempting to disrupt the hunt by putting activists in small inflatables between the harpooners and the whales.

Despite international protests, Japan has this year more than doubled its planned catch of minke whales to 935 and added 10 endangered fin whales, with plans to eventually lift the number to 50, along with 50 rare humpback whales.

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