Japan has signalled that its armed Coast Guard officers will protect its whaling ships from further interference by anti-whaling protestors.

Tokyo says coast guard officers threw so-called "flash-bangs" to warn off environmental activists as they harrassed the main whaling ship the Nisshin Maru in the Southern Ocean.

But Japan's government disputes claims by the head of Sea Shepherd Paul Watson that shots were fired.

In Tokyo, government ministers have backed the actions of the Coast Guard officers, saying they acted in self-defence, and warning that stronger measures may yet be used to protect the Japanese fleet.

Japan's government insists its whaling programs in the Southern Ocean are legal under the provisions of the International Convention on Whaling.

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