Interpol this week placed the head of US-based anti-whaling group Sea Shepherd on an international wanted list at Japan's request, authorities in Tokyo said yesterday.

The Japan Coastguard was informed by Interpol on Thursday about the listing of Canadian Paul Watson, 59, for allegedly conspiring to harass whaling ships in Antarctic clashes in February, a coastguard spokesman said.

The coastguard filed the request with the French-based police service in April as part of Japan's long-running battle with militant environmentalists from Mr Watson's Sea Shepherd Conservation Society.

Kyodo News said Japan had asked Interpol to issue a so-called blue notice, asking national police forces to provide information on Mr Watson's whereabouts and activities, but not a red notice requesting his arrest.

Japan hunts whales under a loophole to an international moratorium that allows the killing of the sea mammals for scientific research, but it does not hide the fact that the meat is later sold in shops and restaurants.

Sea Shepherd has long sought to obstruct Japan's whalers and this year claimed its most successful season yet by preventing the harpoon ships from killing hundreds of the ocean giants.