A Japanese whaling ship and an anti-whaling protest boat collided in the remote, icy seas off Antarctica, with both sides on Monday blaming each other for the crash.
No one was injured, though both ships received minor damage in Sunday's collision - the latest drama in an annual battle between the conservationists and the whalers.
Sea Shepherd, which each year tries to harass the whaling fleet into ending its hunt, said they were the victims of a lengthy attack by the whalers.
The protest group said the whaling vessels spent hours repeatedly dragging steel cables across the bows of the Sea Shepherd's ships in a bid to damage the rudders and propellers.
Japan's Yushin Maru No. 3 then struck Sea Shepherd's Bob Barker when it crossed too closely in front of the protest ship, said Peter Hammarstedt, captain of the Bob Barker.
“It was an unprovoked attack and they did so ruthlessly,“ Hammarstedt told The Associated Press by satellite phone from the Bob Barker.
Japan, meanwhile, says Sea Shepherd is to blame.
The Tokyo-based Institute of Cetacean Research, which sponsors the annual whale hunt, said in a statement that protesters on board two inflatable boats from the Bob Barker dropped ropes in front of the bow of the Yushin Maru, which became entangled in the ship's propeller.
The Bob Barker then drew too close to the Yushin Maru No. 3, colliding with its stern and damaging the whaling ship's hull and railing, the institute said.
Sea Shepherd said the Bob Barker's bow and anchor were damaged.
Federal Environment Minister Greg Hunt has ordered an investigation into the collision.
“This must be a message to both parties - whalers and protesters: These are dangerous waters, nobody can play any games with safety, nobody can play any games with international maritime law,” he told ABC radio.
Japan, which plans to kill about 1,000 whales this year, is allowed to hunt the animals for scientific purposes under an exception to a 1986 ban on whaling. Critics say the program is a cover for commercial whaling, because whale meat not used for study is sold as food.
Last year, Australia went to the United Nations' highest court in a bid to outlaw Japan's annual whale hunt.
Japan says the hunt is legal and produces valuable scientific data.
The International Court of Justice is expected to issue its decision later this year.