Environmental group Sea Shepherd says one of its anti-whaling ships has been attacked by the Japanese whaling fleet in the Southern Ocean.

They say two Japanese harpoon ships crossed the bow of the Sea Shepherd’s Bob Barker ship repeatedly at close range just after 7.30pm (AEDT) on Sunday.

The Sea Shepherd says the Japanese ships dragged steel cable across their vessels to try and disable their propellers and rudders.

The crossing of the bow of the Bob Barker 15 times from port to starboard violates the International Regulations for Preventing Collisions at Sea, the activist group says.

“The assault was an attempt to deter The Bob Barker from blocking the slipway of the Nisshin Maru, where it was preventing the whalers’ ability to load whales poached from the Southern Ocean Whale Sanctuary,” the group says in a statement.

The Sea Shepherd also claims the whaling fleet threw ice at the small boats of The Bob Barker crew and used powerful searchlights, impairing vision.

The group says the Bob Barker is now close to Japanese vessels, Yushin Maru, and Yushin Maru No. 3, and the two harpoon ships are unable to whale.

It is the second time this month the activist group says it has been attacked by the whalers.

Federal Environment Minister Greg Hunt ordered an investigation into earlier claims a Japanese whaling fleet rammed a Sea Shepherd vessel in New Zealand waters on February 2.

Japan’s Institute of Cetacean Research is being contacted for comment.