The anti-whaling group Sea Shepherd Conservation Society says its chase ship has located Japan's whaling fleet near Antarctica and is in pursuit.
In a statement Sunday, the U.S.-based group said that after a week of searching their vessel was 11 kilometers from the Japanese mothership Nisshin Maru and two harpoon vessels and was closing in on them.
Japan has called the Sea Shepherd activists "pirates" and "eco-terrorists" because of their use of aggressive tactics, such as boarding, stink bombs and collisions. But the activists say the whalers are the real "pirates" because their hunt violates international law.
Last month, Paul Watson, Sea Shepherd founder and captain of the Steve Irwin, which has been harassing this year's whale hunt, said the group would halt their pursuit of the Japanese fleet next season if Australia takes legal action against Japan.
Australia's Labor government promised during its 2007 election campaign to begin legal proceedings against Japan at the International Court of Justice. But the government of Prime Minister Kevin Rudd now says it wants to see what progress can be made through diplomacy.
Japan claims that its annual hunt is necessary scientific research permitted under a 1986 ban on commercial whaling. Opponents say lethal methods are unnecessary and claim the expeditions are a cover for commercial whaling. Most of the meat from the hunt ends up on grocery store shelves.
Some information for this report was provided by AFP and Reuters.