Environmental campaigners said yesterday they had prevented Japanese whalers harpooning any of the giant sea mammals for 9 days by engaging them in a 1,000 nautical mile high seas pursuit.

Paul Watson, captain of the Sea Shepherd Conservation Society vessel Steve Irwin said his crew chased the Japanese fleet through ice, rough seas and fog off Antarctica.

"I don't understand where they are running to, they are still going east. We've chased them over 1,000 (nautical) miles (1,852 km) now," Watson said. "And they are still going east and we're still following... they haven't killed any whales in nine days."