CANBERRA: The futuristic anti-whaling protest boat struck by a Japanese harpoon vessel near Antarctica finally sank on Friday, prompting Australia to voice official concern about safety in the remote Southern Ocean.

Senior diplomats in Tokyo made "high-level representations" about safety in Antarctica's frigid waters. They also raised concerns about "spy flights" organized by Japanese whalers from Australian airports to track and foil protesters, Australia's Environment Minister Peter Garrett said.

Canberra, he said, was also keeping open the option of an international legal challenge to Japanese whaling if diplomatic negotiations with Tokyo failed to reach an outcome.