The captain of an anti-whaling boat says a Japanese vessel is trying to destroy his ship's helicopter, because it could be used to locate the rest of the whaling fleet in the Southern Ocean.
The pursuit begain two weeks ago as the the Steve Irwin and the Shonun Maru 2 left Freemantle in Western Australia.
Captain Paul Watson says the Shonun Maru 2 has used water cannon and sonic weapons against his ship.
He says the Japanese harpoon boat has also used a long-range acoustic device to attack the helicopter while it is in flight.
The Japanese Institute of Cetacean Research, which gathers scientific data from the whale hunt, says the attacked the Shonun Maru 2 on Tuesday as the Japanese boat monitored the anti-whaler's movements.
The institute says the Steve Irwin fired on the Japanese vessel with water cannons, green laser devices and bottles filled with butyric acid.
However, Mr Watson says that claim is ridiculous.
He says he used his water cannon and deployed a protection line after his ship was fired upon with water cannon and a military weapon known as a long range acoustic device.
The Steve Irwin is part of the anti-whaling flotilla of the Sea Shepherd Conservation Society which says the Japanese vessel is preventing the ship from getting close to the whaling fleet.