SYDNEY: A space-age powerboat sent to harass Japanese whalers was rammed and sliced in two in its very first clash today, activists said, dramatically escalating hostilities in icy Antarctic seas.

The futuristic Ady Gil trimaran, which holds the round-the-world record and was enlisted by militant activists from the Sea Shepherd Conservation Society for this whaling season, received “catastrophic damage” and was sinking, they said.

All six crew, who earlier hurled stink bombs at the whalers to disrupt their annual hunt, were rescued unharmed by Sea Shepherd’s Bob Barker ship. Activists described the attack as unprovoked and said it was captured on film.

“The Shonan Maru No. 2 suddenly started up and deliberately rammed the Ady Gil ripping 2.4 metres of the bow of the vessel completely off,” a Sea Shepherd statement said.

The whalers accused the Ady Gil’s five New Zealand and one Dutch crew of trying to tangle the Nisshin

Maru’s rudder and propeller with rope, and aiming

a “green laser device” at

its sailors, as well as launching stink bombs.

“The Sea Shepherd extremism is becoming more violent... Their actions are nothing but felonious behaviour,” Japan’s Institute of Cetacean Research said in a statement.

Paul Watson, captain of Sea Shepherd’s Steve Irwin ship and a spokesman for the group, said the annual pursuit had now turned into a “real whale war”. “The Japanese whalers have now escalated this conflict very violently,” he said. “If they think we will be cowed, they are mistaken We now have a real whale war on our hands now and have no intention of retreating.”

Australia said it had no plans to send a vessel to monitor the escalating situation some 1,300 nautical miles south of the Tasmanian capital Hobart as it urged both sides to show restraint. “It’s critical for safety at sea to be the highest priority and for absolute and utmost restraint to be exercised by all parties in this very remote and inhospitable region,” Environment Minister Peter Garrett said.

The Sea Shepherd Conservation Society is a small but militant environmentalist group which specialises in “direct action” to halt marine environmental destruction.

Its activists have harassed the Japanese fleet over the past six hunting seasons, including ramming a whaling vessel, and claim to have saved hundreds of whales.