The fleet's factory ship, the Nisshin Maru, was trying to be refuelled by the Panamanian registered ship, the Oriental Bluebird.

Greenpeace says the refuelling goes against the Antarctic Treaty and that the Oriental Bluebird should not even be there, because it is not part of the Japanese fleet.

Dave Walsh from Greenpeace says after efforts by the Esperanza to get between the two other vessels, the protest became too dangerous.

"They've gone ahead with refuelling now - it was too dangerous for us to continue blocking them because they were pushing their two ships together, which was quite a dangerous manoeuvre with people sitting between on a boat," he said.

"So they are refuelling at this point and if they move on again, we'll be with them and if they try whaling again, we'll be there to stop them."- Source: By Australian Broadcasting Corporation