The militant environmental group Sea Shepherd said Monday that it had located the Japanese whaling fleet near Antarctica and threatened to ram them if they resumed slaughtering the giant sea creatures.

Paul Watson, captain of the Sea Shepherd's ship, said the leading Japanese vessel, the Nisshin Maru, was now outside the hunting area and had not killed any whales in the past 48 hours.

"I think they're running scared really," he told AFP via telephone from on board the ship.

This handout picture shows the Japanese whaling vessel Yushin Maru, a catcher boat of the Japanese whaling fleet, as seen from the Greenpeace ship Esperanza, in the Southern Ocean 12 January 2008. Greenpeace reported it is carrying out non-lethal research on whale populations in the Southern Ocean Whale Sanctuary from their ship, Esperanza, while en-route to stop a Japanese whaling fleet who intend to kill 935 Minke and 50 endangered Fin whales.

"When we found them originally they were down by the icebergs and as we were moving in they started running and they've been running ever since."

In response to a question, Watson confirmed he would ram the Japanese fleet if his ship came upon them killing whales.

But he added: "It is something we have to do very carefully because it's very remote and rough waters down here."

Australia, which has led international opposition to the hunt, has warned environmentalists against dangerous manoeuvres in the ice-cold conditions due to the difficulty of any rescue operation.

But Watson said his group felt empowered to ram the boats because of global opposition to Japan's plans to kill 1,000 whales.

Tokyo exploits a loophole in a 1986 international moratorium on commercial whaling to kill whales for what it calls scientific research, while admitting the meat from the hunt ends up on dinner plates.

"We didn't come down here to protest, really we came down intervene and to disable them if need be," Watson said. "As long as we don't injure any of their crew. We certainly can damage their equipment."

The global environmental pressure group Greenpeace also has a vessel in the area tracking the whalers.

Karli Thomas, expedition leader on the Greenpeace ship Esperanza, said her boat had caught up with the Nisshin Maru early Saturday.

"As long as we can keep her on the run we can stop the entire fleet from catching whales," she told AFP.

Thomas said the Greenpeace activists were prepared to put their boats and themselves between the harpoons and the whales if the Nisshin Maru turned back to the hunting ground.

"We'll do anything we can within the boundaries of non-violent direct action to stop them from killing whales," she said.