CANBERRA (Reuters) - Japanese whalers and protesters in the icy Southern Ocean charged each other with "terrorism and piracy" on Wednesday, as two activists remained locked up on a Japanese ship after boarding the vessel in a protest action.
Whaling has halted while the two men are being held on board and will not re-start until they have been handed over, Japanese Fisheries Agency official Takahide Naruko told reporters.
Naruko, head of the agency's Far Seas division, declined to say how many whales had been taken before the suspension.
The whalers said they would only release the two men if the militant Sea Shepherd Conservation Group promised not to take any "violent action" against their ship and keep the protest ship Steve Irwin 10 nautical miles from the whaler Yushin Maru No.2.
Steve Irwin captain Paul Watson, who last year threatened to ram the Japanese flagship and collided with a whale hunter, rejected the conditions.
"Using hostages to make demands is the hallmark of terrorism and Sea Shepherd has no interest in negotiating with terrorist groups," Watson said in a statement. "The hostages must be released unconditionally."
Australia's Foreign Minister Stephen Smith said in a statement: "Neither captain involved should set conditions on the return beyond those necessary to ensure the safe return of the two men."
Japan's Chief Cabinet Secretary Nobutaka Machimura said he did not expect the incident to have any effect on diplomatic relations.
A letter from Japan's Institute of Cetacean Research told the protesters to "use your zodiac boat to rendezvous with Yushin Maru No.2 without carrying any dangerous items for attacks."
The letter also said the protesters must stop filming, photographing and protesting against the whalers.
"If you accept the above ... we will provide you detailed information for the release of the two individuals, rendezvous times and position," said the letter sent to the Steve Irwin, a ship named after the late naturalist and television celebrity.
The Institute's letter called the anti-whaling activists "terrorist," for illegally boarding a ship on the high seas, in what could be seen as an act of "piracy."
Australian Benjamin Potts and Briton Giles Lane boarded the whaling vessel late on Tuesday. Sea Shepherd said they were delivering a letter telling the crew they were "illegally killing whales."
Sea Shepherd's Watson said the men were tied to a radar mast and dunked in icy water before being taken below decks.
The two men were initially tied up, the Fisheries Agency's Naruko said on Wednesday, but were then held in an office on the ship.
"When we realized that the two activists' objective had been to hand over a letter of protest, we decided to return them to Sea Shepherd," the agency said in a news release.
Japanese officials said the activists boarded the whaler after making attempts to entangle the propeller of the vessel using ropes and throwing bottles of acid onto the decks.
Sea Shepherd said the pair only threw stink bombs of rancid butter.
Despite a moratorium on whaling, Japan is allowed an annual "scientific" hunt, arguing whaling is a cherished cultural tradition and the hunt is necessary to study whales. Its fleet has killed 7,000 Antarctic minkes over the past 20 years.
Japan plans to hunt almost 1,000 minke and fin whales for research over the Antarctic summer, but has abandoned the cull of 50 humpback whales after international condemnation and a formal diplomatic protest by 31 nations.
Watson said the two activists were "roughed up" by the Japanese crew. But the whalers said the men were "treated humanely," and provided with a warm meal and bath.
CALL FOR RESTRAINT
Smith said the Japanese government wanted the two men transferred back to the Steve Irwin and were instructing the whaling vessel to secure the transfer.
But the pair could be handed to an Australian fisheries ship en route to the area. The ship is attempting to gather evidence for an international court challenge against Tokyo's annual "scientific" whaling program.
"From the very first day, I urged all parties in this matter to exercise restraint. It is quite clearly the case that restraint hasn't occurred here," said Smith.
The two anti-whaling protesters were detained inside Australia's declared Antarctic waters and a southern whale sanctuary declared by Canberra but not recognized by Japan.
Donald Rothwell, an Australian international law expert, said boarding another vessel on the high seas could be seen by a court as an act of piracy or worse. "It could also be seen possibly as an act of terrorism," Rothwell said.
(Additional reporting by Isabel Reynolds in Tokyo; editing by Michael Perry and Jerry Norton)