Sydney (AFP) - Militant environmentalist group Sea Shepherd and Japanese whalers on Monday traded accusations of a potentially dangerous attack in the perilous Southern Ocean.
Sea Shepherd said two Japanese harpoon ships attacked their Bob Barker vessel on Sunday night, using steel cables in an attempt to jam its propellers and rudders from close range in violation of laws aimed at preventing collisions at sea.
But officials in Tokyo in charge of the hunt said it was their ships that had been ambushed.
Bob Barker captain Peter Hammarstedt said he had been tailing the Japanese factory ship Nisshin Maru since Sunday morning but the harpooners waited until night fell -- "launching their onslaught under the cover of darkness".
High-seas confrontations are common between Sea Shepherd and the Japanese, who hunt whales off Antarctica under a "scientific research" loophole in the moratorium on whaling. Sunday's incident marks the second such showdown in a month.
"We maintain unwavering dedication in the face of an increasingly vicious onslaught from the poachers, the last line of defence standing between these criminals and the protected whales they are targeting to kill," Hammarstedt said.
The captain said he radioed the Japanese ships to inform them that his operations were "completely lawful and that any aggressive action on their part would be reported to the Australian government and New Zealand Search and Rescue".
"I have nine Australians and one New Zealander on board as part of my brave crew who have endured this ruthless assault," he said.
Sea Shepherd Australia director Jeff Hansen said both Australia and New Zealand had challenged Japan's whaling programme at the International Court of Justice.
"So where are these governments now, when their citizens... are under attack from these poachers?" he asked.
During the incident Sea Shepherd said crews in its small boats were pelted with ice by the Japanese, who also shone blinding searchlights on the Bob Barker's bridge to allow the Nisshin Maru to escape.
The factory ship was now being tracked by Sea Shepherd's two other vessels, the Sam Simon and the Steve Irwin. The Bob Barker continued to shadow the harpoon ships, claiming they were currently "unable to whale".
In Tokyo, a Japanese fisheries agency official said the campaigners had been the aggressors.
"The two Japanese ships were faced with a dangerous act by Sea Shepherd on Sunday," he said on condition of anonymity.
"The propellor was caught with a rope thrown by Sea Shepherd while the hull was damaged. But no one was injured and there has been no problem with navigation.
"The whaling operation is going on. We were not responsible. Sea Shepherd members should be held responsible."
It is the second time the two groups have come to blows this month, with Sea Shepherd claiming the Bob Barker was struck during a coordinated attack by the Japanese a few weeks ago.
Tokyo confirmed that collision but accused Sea Shepherd of throwing rope at its ships.
In 2010 a collision resulted in the sinking of Sea Shepherd's speedboat Ady Gil.