Japanese whaler accused of ramming.
Sea Shepherd founder Captain Paul Watson said by satellite telephone that the Japanese ship rammed the conservationists' ship the Bob Barker and tore a gash in the hull above the water line, the Associated Press reported.
No one was injured in the incident, which happened about 300 kilometres off Cape Darnley, in the Australian Antarctic Territory, at 1509 AEDT on Saturday, the Sea Shepherd group said in a statement.
The organisation claimed the Yushin Maru 3 "intentionally" rammed the Bob Barker.
The anti-whaling craft had been actively blocking the slipway of the Nisshin Maru, the Japanese whaling fleet's factory ship, when the collision occurred.
The Bob Barker, named after a US game show host who donated millions to buy it, was not in danger of sinking, the AP reported.
It was the second major clash between the conservationists and Japanese whalers this year, after the Ady Gil sank following a collision with a Japanese whaling ship in the Southern Ocean on January 6.
Japanese officials were not immediately available to comment.