New pictures expose the gory reality of Japan's so-called "scientific" whale hunt in the Southern Ocean, with a slaughtered adult minke whale and calf being hauled on board a Japanese factory ship.

The release of the photos marks a significant shift in whaling politics, for they were taken not by the environmental activists who spent much of January harassing the whalers on their Antarctic hunt but by officials working for the Australian government.

They were put into the public domain by the eco-friendly administration of the new Labor premier, Kevin Rudd, accompanied by withering comments from Australian ministers.

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For a government to become so strongly involved raises the stakes considerably in a dispute in which most of the international community is ranged against Japan.

It provoked anger in Tokyo and a warning to Australia from a Japanese official that this was "dangerous emotional propaganda that could cause serious damage to the relationship between our two countries".

But there was as much, if not more fury, at the pictures in Australia. Peter Garrett, the Environment Minister, and a former member of the rock group Midnight Oil, said: "It is explicitly clear from these images that this is the indiscriminate killing of whales, where you have a whale and its calf killed in this way." He said he felt "sick and sad" looking at them and added: "To claim that this is in any way scientific is to continue the charade that has surrounded this issue from day one."

The images include footage of a harpoon being shot into a whale, which is then hauled on to the ship. One photo shows two whales – one far smaller than the other – being dragged by ropes up a ramp.

The row comes as the Humane Society International urges the Australian government to launch a case against Japanese whalers in the International Tribunal of the Law of the Sea. Japan has defied the international moratorium on commercial whaling which has been in place since 1986 by claiming that its whale hunts are carried out for scientific purposes. This season it is seeking to kill up to 935 minke whales and 50 larger fin whales.

Last month activists from two anti-whaling groups, Greenpeace and the Sea Shepherd Conservation Society, spent weeks trying to disrupt the hunt with their vessels Esperanza and Steve Irwin. Many of their pictures were flashed around the world. But perhaps of more long-term significance was the fact that this time Australia sent a fisheries and customs patrol ship, Oceanic Viking to the Southern Ocean to gather photographic and video evidence about Japan's hunt, for use in a possible legal challenge.

The resulting pictures caused a strong reaction in Tokyo yesterday.

Hideki Moronuki, chief of the Japanese Fishing Agency's whaling section, denied that the photograph depicted a baby whale, and accused Australian officials of coming dangerously close to the whaling ships to take the images.

"The fleet is engaged in random sampling, which means they are taking both large and small whales," he said. "This is not a parent and calf."