Japanese authorities have lashed out at the Sea Shepherd anti-whaling group after Japanese whaling crewmen were reportedly injured in a high-seas clash with the activists.
Japan's Institute of Cetacean Research said three crew suffered face and eye injuries from butyric acid fired by anti-whaling protesters during their latest encounter with the Japanese whaling fleet in the Southern Ocean.
The confrontation reportedly lasted several hours between two Sea Shepherd boats - the Steve Irwin and the Bob Barker - and four Japanese vessels.
Glenn Inwood, spokesman for Japan's Institute of Cetacean Research (ICR), said the injuries were not serious, but he warned the acid could cause temporary blindness.
A crew member on the Steve Irwin, the Sea Shepherd flagship, said butyric acid was a "harmless" non-toxic liquid made from rancid butter.
"You can handle it, and it's not corrosive," first mate Locky Maclean told The Associated Press.
Mr Maclean said the Nisshin Maru, a whaling factory ship, started the five-hour altercation when it turned its water cannons on the activists' vessels.
He said the ship's military acoustic device was also aimed directly at the Sea Shepherd's helicopter pilot.
ICR said in a statement that the protesters targeted the Japanese ships Shonan Maru No 2 and Nisshin Maru, dragging wire ropes across their bows in a bid to tangle and disable their rudders and propellers.
The crew of the Shonan Maru No 2 said they were targeted with a high-powered laser weapon, while smoke bombs and red dye projectiles were launched at the Nisshin Maru.
The factory ship also exchanged close-range water cannon fire with the Sea Shepherd vessels.
The injuries were the first sustained by Japanese whalers this year in confrontations with Sea Shepherd.
The whalers and the activists have been involved in two collisions. Sea Shepherd's vessels came off worse on both occasions, with the Ady Gil later sinking and the Bob Barker sustaining hull damage.
Japan's Fisheries Minister Hirotaka Akamatsu told reporters on Friday he was "full of rage" at the protesters' latest actions.
"I could not believe they did such a thing," he said.
Chief Cabinet Secretary Hirofumi Hirano said that the activists' actions were unforgivable.
"Thank God it did not result in serious injuries, but it is extremely regrettable," he told reporters.
Steve Irwin captain Paul Watson said the success of Sea Shepherd's methods were borne out in the fact that a week had passed in which no whale was killed by Japanese whalers.
"Our goal now is to make it two weeks and then three weeks. We will not tolerate the death of a single whale," he said in a statement.
"If they attempt to kill and transfer a whale to the Nisshin Maru there will be inevitable collisions, because we will neither move out of harm's way nor cease blocking the slipway. That I can promise."
