The three men, from Western Australia, Geoffrey Tuxworth, Simon Peterffy and Glen Pendlebury, had counted on being captured and had planned the hunger strike all along, according to the environmental group, Forest Rescue Australia.

They boarded the Japanese whaling vessel, Shonan Maru 2, off the southwest coast of WA, near Bunbury, on Saturday night. Two of the men suffer from medical conditions and are without their medication.

Forest Rescue Australia spokesman Rowan Davidson, said the protesters had been detained by the Japanese vessel’s crew and could be taken to Tokyo to face piracy and trespass charges.

However, the Australian Federal Government admits it does not know where the Japanese whaling security ship has disappeared after the protesters climbed aboard.

Attorney-General Nicola Roxon says said although the government is doing what it can to help the whaling protesters aboard Shonan Maru No. 2, it had become a diplomatic issue.

She said ”firm” representations had been made to the Japanese government, though they were no wiser about the whereabouts of the whaling ship security vessel, or the men.

“We have asked to be able to speak directly to the three men … That hasn’t yet happened,”  Roxon said.

”Any vessel is not required to give us the details of their particular vessel at any time.

”The primary concern is for the health and wellbeing of the three men but the legal options available to Australia are limited when this action occurred outside our territorial waters.”

Davidson, from Forest Rescue Australia, said Tuxworth, Peterffy and Pendlebury’s aim was to stop the whaling ship from tailing the Sea Shepherd Conservation Society’s anti-whaling flagship, the Steve Irwin.

The men surmounted razorwire and spikes to board the ship and deliver a message: “Return us to shore in Australia and then remove yourself from our waters.”

However the Shonan Maru No.2 was last seen yesterday afternoon persisting with its pursuit of the Steve Irwin, with the Australians still on board.

Australian opposition leader Tony Abbott has urged the Government to send a customs vessel to “keep the peace” in the Southern Ocean, saying it is the government’s job to “help Australians in trouble”.

A spokesman for Japanese Whaling, Glen Inwood, from the Institute of Cetacean Research, says the men should prepare to be aboard the Shonan Maru No. 2 for the next couple of months.

“Not only are they facing that, but they risk being taken to Japan to be tried for trespassing, or for other charges,” he said. He added the men are being well looked after.

There is a dispute as to where the Shonan Maru No. 2 was when the men climbed on board. Inwood said the men had boarded the Japanese whaling vessel well outside Australian territorial waters – about 40km from the coast. The Sea Shepherd and Forest Rescue say the incident happened 16.2 miles off the coast – outside territorial waters but inside Australia’s 24-mile contiguous zone.

Watch the video of the protesters boarding Shonan Maru 2 here: