Greenpeace says it has driven the Japanese whaling fleet out of Antarctic hunting grounds after a dramatic, 24 hour chase through thick fog and rough seas.

The Greenpeace ship located the six Japanese whalers on Saturday after 10 days of scouring the icy reaches of the Southern Ocean.

The environmental group plans to harass the fleet and disrupt its plan to kill nearly 1,000 minke and fin whales by placing volunteers in inflatable boats between the whales and the whalers' harpoon guns.

Sara Holden is Head of the Whales Project at Greenpeace.

Greenpeace has been chasing the fleet night and day, and now we are well outside the hunting zone. Conditions are getting more difficult, but we are determined to keep up the chase for as long it takes.

Greenpeace says it suspects that the whaling fleet is planning to refuel soon and offload whale meat that has already been processed onto a Panamanian-registered tanker, a ship not licensed to be part of the whaling fleet.

It says that the refuelling process between the tanker and the whaling vessels could be a threat to the pristine environment.

Commercial whaling has been banned since 1986, but Japan's whaling fleet operates under a clause in International Whaling Commission regulations that allows the killing of whales for scientific research purposes.

Tokyo has staunchly defended its annual kill of more than 1,000 whales as crucial for research purposes.

It has killed around 7,000 minke whales in the name of research over the past two decades.