Anti-whaling vessels from the Sea Shepherd organisation have collided with the whaling ship Nisshin Marym.
The Institute of Cetacean Research (ICR), which owns the Japanese ship, said in a statement its vessel was rammed at least five times by Sea Shepherd vessels Steve Irwin, Bob Barker and Sam Simon in the Southern Ocean yesterday.
The incident occurred as the Nisshin Marym came along its supply tanker for refuelling, ICR said.
There were no injuries to the crews of the Nisshin Marym or its supply tanker.
ICR claimed video of the incident showed Sea Shepherd deliberately ramming its vessel.
Sea Shepherd founder Paul Watson said it was "ludicrous" for the Japanese to say Sea Shepherd were the aggressors.
"The Nisshin Marym is 8000 tonnes and our vessels are 500 tonnes. We would cause absolutely no damage to them if we were to do that.
"What we were doing was holding our positions to prevent them from refuelling illegally and it was the Nisshin Marym that tried to move us out of those positions by hitting us."
Sea Shepherd vessels Sam Simon and Bob Barker were both hit twice and sustained serious damage.
"The Sam Simon had its radar crushed and there was a big crack on the hull. On the Bob Barker there's now a crack across the deck so you can see through the galley floor into the engine room. They knocked down the mast, destroyed the radar and buckled the helicopter deck."
Mr Watson said Sea Shepherd crew had taken their own footage of the incident which showed their ships were following collision regulations and the Nisshin Marym that was at fault.
They would present the footage to the Australian Maritime Safety Authority and the Dutch government, because they are Dutch and Australian vessels.