Anti-whaling activists have called for Australia to send a naval vessel to the Southern Ocean after a confrontation in which they said a Japanese whaling ship collided with two of their protest vessels, damaging their flagship.
"The Nisshin Maru has rammed the Steve Irwin and the Bob Barker, but both vessels continue to hold their positions," Paul Watson, the founder of the Sea Shepherd Conservation Society which runs the protest boats, said.
Watson also accused Japanese coastguard personnel of throwing concussion grenades at their protest ships during a confrontation in the frigid waters near Antarctica and said the Bob Barker was taking on water in its engine room at one stage.
Australia said it was confirming the report of the incident. Neither the Japanese Government nor its whaling authority immediately responded to the Sea Shepherd's account of the clash.
Sea Shepherd director Bob Brown told journalists in Melbourne the two Sea Shepherd ships had been repeatedly rammed and called on Australia's Government to dispatch a naval ship to the area to calm the tension.
"It is illegal to be ramming ships in any seas anywhere on the planet. It is illegal for a tanker to be carrying heavy fuel oil into Antarctic waters under international law," Brown said.
The Sea Shepherd group has clashed with the Japanese fleet for nine whaling seasons in the summer, and has lost one of its ships, the high-speed trimaran Ady Gil which sank after a collision with a whaler in January 2010.
In the latest incident, the activists had been attempting to prevent the 8,000-tonne Japanese factory ship Nisshin Maru refuelling from a tanker, Sun Laurel, when the collision occurred.
Australia has filed a complaint against Japan at the world court in the Hague to stop Southern Ocean scientific whaling. A decision could come this year.
"The government condemns so-called 'scientific' whaling in all waters and we urge everyone in the ocean to observe safety at sea," Australia's Environment Minister Tony Burke said in a statement.
Japan introduced scientific whaling to skirt a commercial whaling ban under a 1986 moratorium. It argues it has a right to monitor the whales' impact on its fishing industry.
A US appeals court in December issued an injunction ordering Sea Shepherd and Paul Watson not to physically attack or endanger the five-ship Japanese whaling fleet.
Sea Shepherd said in a post on Facebook this afternoon it is "getting nasty in the Southern Ocean".
The Bob Barker was taking on water in its engine room and the vessel put out a mayday call, Watson told ONE News from on board the Steve Irwin after the collision.
But he said the leak had been controlled and the crew was working to restore power to the ship which is disabled with its machinery shut down.
"The Nisshin Maru struck the Steve Irwin twice and struck the Bob Barker multiple times, and then also smashed into the side of their own tanker, the Sun Laurel, causing damage to the Sun Laurel," he said.
"We've been holding our position so they just muscled their way in by just coming in and hitting the Steve Irwin to knock it aside.
"And then they hit the Bob Barker and drove it into the side of the tanker, the Sun Laurel, and pinned it there and then ran over the top of it. We actually had the bow of the Nisshin Maru towering over the wheel house of the Bob Barker."
Watson said none of the 42 people on board the Steve Irwin or the 34 on the Bob Barker was injured.
He said: "We filmed the Nisshin Maru coming up behind us and they just kept moving closer and closer. And they didn't stop and struck the Steve Irwin and just kept coming on to the Bob Barker."
Watson said it is illegal to transfer heavy fuel below 60 degrees "and we're 300 miles below 60 and we're about 180 miles from the Australian Davis research base."
Director of Sea Shepherd Australia Jeff Hansen said the South Korean-owned, Panamanian registered Sun Laurel had already spilt oil into the sea below 60 degrees and inside the Australian Antarctic Territorial waters.
It was now attempting to refuel the Nisshin Maru with heavy fuel oil.
This is a violation of the Antarctic Treaty, Australian law and international law, he said in a statement.
"We are deeply concerned of the potential for a massive oil spill and ecological disaster in the pristine Antarctic wilderness, off Australia's Antarctic coast in Australian waters."
Captain Siddharth Chakravarty aboard the Steve Irwin said: "This situation has gone too far. The recklessness of the Japanese Whaling Fleet and the Sun Laurel have put Antarctica's rich environment at grave risk for an ecological nightmare.
"The time has come for the Australian government to intervene and and put a stop to this insanity."