The key Japanese whaling factory ship, Nisshin Maru, has outpaced a Sea Shepherd pursuit in the Antarctic, as the whalers turn tables on the activists.

After running for two days out of its whaling grounds with Sea Shepherd ships on its stern, Nisshin Maru sped beyond the reach of the group's helicopter and disappeared, director of ship operations, Peter Hammartsedt, said.

"The Steve Irwin's helicopter no longer has the Nisshin Maru in sight," Mr Hammarstedt said. "We've never really seen it go this fast before."

Instead, he said each Sea Shepherd ship was being tailed by a Japanese whaling fleet vessel, meaning Nisshin Maru could be informed to avoid the activists.

The factory ship also had one harpoon vessel, the Yushin Maru, steaming alongside it and able to resume whaling, Mr Hammartsted said.