The environmental group Greenpeace has claimed to have driven Japan's controversial whaling fleet out of Antarctic hunting grounds after a dramatic chase through thick fog and rough seas. Activists have promised to harass the Japanese fleet and disrupt its plan to kill nearly one thousand minke and fin whales. Phil Mercer in Sydney reports.

The Greenpeace ship Esperanza found six Japanese whaling vessels over the weekend after 10 days of scouring the icy waters of the Southern Ocean.

The global environmental group has promised to use nonviolent action to stop the ships from killing whales.

A Greenpeace spokeswoman, Sarah Holden, says the Japanese vessels "scattered and ran" when they realized the Esperanza was heading toward them...

"They sent one of the hunter vessels to check us out and the rest of them just ran right in front of us and we are going further and further north," she said. "We've chased them out of the whaling grounds. We're very happy about that."

Greenpeace's success could, however, be short-lived.

The Japanese fleet is expected to re-fuel from a tanker in the area before returning to the hunting grounds.

Japan plans to catch 935 minke and 50 fin whales over the Antarctic summer for what Tokyo has says are research purposes.

Under worldwide pressure, Japan has given up plans to include 50 humpback whales in this season's hunt.

The Australian government also has a ship shadowing Japan's whaling fleet, and air patrols are watching the hunt.

If they find evidence that Japan is violating international rules on whaling, the Australian government could mount an international court challenge against the whalers.

Japan argues that years of a global hunting ban have allowed whale populations to grow enough to allow hunting. Many Japanese say that hunting and eating whales are part of their traditions and should be allowed. Other governments and many environmental groups say, however, that whale populations are too fragile to tolerate hunting. They also complain because Japan sells the meat of whales it harvests for research.