Anti-whaling activist group Sea Shepherd claims its ships are again being attacked by Japanese whalers.
On its Twitter and Facebook pages, the anti-whaling marine wildlife conservation organisation says the Japanese factory ship Nisshin Maru is attempting to refuel off a tanker, Sun Laurel in the Southern Ocean.
They say it has "rammed the (Sea Shepherd ship) Bob Barker twice, shoving it into the side of the tanker.
"The Nisshin Maru threw a flash bang grenade that exploded off the port stern of the Sun Laurel."
The posts say the organisation's two other ships, Sam Simon and Steve Irwin, have flooding in their engines from Nisshin Maru's water cannons.
"The Steve Irwin's water cannons have been engaged, the crew have been instructed not to aim them at any people on the poaching vessels."
Sea Shepherd said the action is being watched by Shirase, a large icebreaker operated by the Japan Maritime Self Defence Force. The 12,500-tonne Shirase can carry 250 people and three helicopters.
Australian environment minister Tony Burke issued a please-explain to Japan about the ship's role, suggesting it was exploiting a loophole by assisting the Korean tanker rather than the Japanese whalers directly.
"Japan has told the government that the Shirase is not involved in supporting their so-called scientific whaling fleet," Mr Burke said in a statement.
"It's true that up until now the Shirase has been probably the only large vessel Japan sends to the Southern Ocean with a genuine research role.
"But the reports today of helicopters flying from the Shirase to the South Korean tanker being used for the refuelling of the Japanese whaling fleet mean there is a further question to be answered.
"If there is no link or support to the Japanese whaling fleet, has there been a link, support or transfer of Japanese personnel to the South Korean tanker?
" ...The tanker is the life blood for the rest of this disgusting operation.
"Japan needs to confirm that there is no link between the Shirase and the tanker."
Japanese consul-general in Melbourne Hidenobu Sobashima told Fairfax he was unable to comment on the movement of ships.
The Japanese government has repeatedly called for Sea Shepherd to end its obstruction of the whaling fleet.
It said the activists endangered the lives of the crew, and property, and safe navigation at sea.
Sea Shepherd is an organisation that, according to its website, "uses direct-action tactics to investigate, document, and take action to expose and confront illegal activities on the high seas".
- © Fairfax NZ News