The Japanese Coast Guard has obtained an arrest warrant for the leader of the Sea Shepherd environmental group for its disruption of Japan's annual whale hunts, local media are reporting.

The move would be the latest in an increasingly aggressive campaign against the radical conservationists by Tokyo, which accuses them of endangering lives during the Antarctic hunt. US-based Sea Shepherd has long insisted the Japanese fleet is conducting banned commercial whaling under the guise of scientific research.

The warrant is for Paul Watson, the Canadian founder and president of the Sea Shepherd Conservation Society, on suspicion of assault and obstruction of business, Kyodo News agency reported, citing investigative sources. It did not say which court issued the warrant.

The Japanese Coast Guard wants Watson placed on the wanted list of Interpol, the international police agency, national broadcaster NHK reported.

Watson captains one of the Sea Shepherd ships that each year seeks to disrupt Japan's whaling activities in the Antarctic seas by trying to disable or cut off the Japanese ships.

A Coast Guard spokesman said the organisation does not comment on arrest warrants it has obtained.

Japan has recently struck back at activists that try to disrupt its whaling activities. Last month a protester that had climbed aboard a whaling vessel in this year's hunt was formally arrested, and Tokyo issued a request to Australian authorities that led to a police search of Sea Shepherd anti-whaling boats.

Confrontations between Sea Shepherd boats and Japanese vessels have at times turned violent. In the hunt that ended earlier this year, there were several collisions in the icy waters, and a small protest boat sunk.

Activists from the group try to obstruct whaling ships by cutting them off, dangling ropes in the water to snarl their propellers, or throwing containers of rancid butter. The whalers have responded with water canons and sonar devices to disorient the environmentalists.

Last month, Japan's coast guard said it had formally arrested a member of Sea Shepherd who climbed onto a Japanese whaling vessel from a Jet Ski. Peter Bethune, a 44-year-old New Zealander, was held on the boat and arrested upon its return to Tokyo.

Japan each year hunts hundreds of mostly minke whales - which are not an endangered species -- in Antarctic waters under a research program, an allowed exception under international law. Excess meat is sold for consumption, leading critics to call the program a cover for commercial hunts.

- AP