New Zealand anti whaling activist Peter Bethune has reportedly been handed over to Tokyo authorities by the Japanese coastguard.
The 44-year-old activist is facing up to three years in jail is he's indicted and found guilty of trespass after he secretly boarded a Japanese whaling ship last month.
In mid-February he climbed aboard the Japanese ship before dawn from a jet ski with the stated intention of making a citizen's arrest of captain Hiroyuki Komiya for what he said was the attempted murder of his six crew.
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Bethune also presented the Japanese whalers with a $US3 million ($A3.28 million) bill for the futuristic carbon-and-kevlar trimaran Ady Gil, which sank in the icy waters a day after the collision on January 6.
Earlier New Zealand Prime Minister John Key said his Foreign Minister Murray McCully had kept in contact with the Japanese ambassador, and diplomats are playing their part in Japan.
"The situation is...he's going to be charged across a range of different sort of breaches of the law, potentially," Key told TVNZ's Breakfast program on Monday.
"Peter Bethune is obviously a person who cares deeply about what he's doing, he's also a person who made it quite clear when he got on board that boat that he didn't want to be taken off, he did want to be taken to Japan. So clearly he has thought all this through and has thought the exposure that he will get for this warrants his activities."
Other than consular support there's little the government can do, Key said.
"We can't actually interfere in the Japanese legal process."
The group declared an end to this season's three-month pursuit of Japanese harpoon ships in Antarctic waters on February 27, saying it has been the most successful campaign yet because it stopped all whaling on 33 days.
