Whaling protesters: Ship is hunting us

The anti-whale hunting group the Sea Shepherd says a Japanese security ship has illegally followed them into French Antarctic waters and fired "a military-class weapon" at their helicopter.

The Sea Shepherd Conservation Society says the Japanese ship, the Shonan Maru No 2, as been following its vessel, the Steve Irwin, for nine of the 10 days it has been sailing since leaving Fremantle.

It says the Shonan Maru has been constantly reporting the Steve Irwin's location, preventing it closing in on the Japanese whaling fleet.

A Sea Shepherd spokeswoman said the Steve Irwin entered French Antarctic territorial waters with permission from the French base at Dumont Durville, in a bid to lose the Shonan Maru.

The French base confirmed that the Japanese ship neither requested nor received permission to enter French waters. The spokeswoman said the Steve Irwin helicopter then flew back to film the Shonan Maru in its pursuit.

"In response, the crew of the Japanese ship activated their long-range acoustical device (LRAD) at the Sea Shepherd helicopter," she said in a statement. "LRAD is a military-class weapon."

Helicopter pilot Chris Aultman said the use of the weapon was extremely irresponsible.

"That device can cause nausea and disorientation, and the use of it against an aircraft is extremely dangerous," he said in the statement.

The Sea Shepherd helicopter returned to the Steve Irwin for safety, at which point the Shonan Maru increased speed and its crew aimed water cannons at the helicopter on the landing pad, the spokeswoman said.

Steve Irwin captain Paul Watson said the situation was now very dangerous.

"We have deliberately led the Japanese ship into thick ice in order to lose them in the ice. The icebergs could easily damage either vessel."

Sea Shepherd said it had reported the incident to the French authorities.

The Steve Irwin ship was undamaged, but the pursuit was continuing.

- AAP