An anti-whaling group says its members threw stink bombs at a Japanese whaling ship in Australian waters off Antarctica.

The Sea Shepherd Conservation Society said Saturday the crew on its ship, the Steve Irwin, hurled bottles containing rancid butter at a Japanese research whaling ship, the Kaiko Maru. The incident took place Friday north of the Mawson Peninsula, which is in Antarctic territory claimed by Australia.

A Japanese government-backed whaling body, the Institute of Cetacean Research, said the conservationists' boat rammed the whaling vessel. The captain of the conservationists' boat, Paul Watson, said the two ships collided but that neither sustained serious damage.

Watson, who is also the Sea Shepherd Conservation Society's founder and president, said the group is seeking to push Japanese whalers out of Australian waters.

Japan claims that its annual whale hunt in waters near Antarctica is necessary scientific research as permitted under a 1986 ban on commercial whaling. Opponents say the research expeditions are a cover for commercial whaling.

Last month, Australia announced a plan to invest millions of dollars into whale research, to show Japan that lethal methods are scientifically unnecessary.

The international headquarters of the Sea Shepherd Conservation Society is in the U.S. state of Washington. It also has offices in several other countries, including Australia.

Some information for this report was provided by AFP, AP and Reuters.