Japanese coastguards have arrested a New Zealand activist belonging to the Sea Shepherd anti-whaling organisation.

In February, Pete Bethune boarded a Japanese whaler in a protest action. He has since been held in custody on board the ship. The harpoon ship docked in Toyo on Friday, and Mr Bethune was immediately handed over to the coastguards.

Mr Bethune was the skipper of Sea Shepherd’s futuristic vessel, the Ady Gil, which was destroyed in a collision with a Japanese ship two months ago. In protest, last month he approached another Japanese vessel on a jet ski and climbed on board, intending to make a citizen's arrest on the captain he held responsible for the crash. The New Zealander faces a maximum three-month jail sentence for boarding the vessel illegally.