By Rob Taylor CANBERRA, Feb 7 (Reuters) - Australia released on Thursday pictures of whales killed by a Japanese fleet in the Southern Ocean ahead of a possible legal challenge to stop the annual slaughter, fueling public anger over the practice. A photo of an adult minke whale and her calf being towed up the rear ramp of a Japanese factory processing ship in Antarctic waters prompted headlines including "They call it science". "When I saw the photos I just felt a bit of a sick feeling as well as a sense of sadness," Environment Minister Peter Garrett said. One image showed what appeared to be the young whale's intestine spilling out from an explosive harpoon wound. "This isn't about science, it isn't about research. They're calling it science, but really it's killing whales," Garrett said.Japan plans to hunt almost 1,000 minke and fin whales for research over the Antarctic summer. Despite a moratorium on whaling, Japan is allowed an annual "scientific" hunt, arguing whaling is a cherished tradition and the hunt is necessary to study whales. Its fleet has killed 7,000 Antarctic minkes over the past 20 years. The photographs were taken by an Australian fisheries and customs patrol ship sent to the Southern Ocean to gather photo and video evidence of Japan's scientific whaling for a possible challenge in international legal tribunals. In one photo a banner hangs from the back of the factory ship saying it is conducting "legal research under the ICRW (International Convention for the Regulation of Whaling)". The mother and the calf, which experts said was under a year old, were tied at the tail by cables as Japanese crew in hard hats looked down on Australian customs officers in an orange inflatable boat. Another photograph shows a whale tethered to harpoon lines at the bow of a whaling ship. Anti-whaling activists left the Southern Ocean last week to refuel in Australia and the hardline Sea Shepherd protest group plans to return south in another week to harass the six-ship Japanese fleet. "It's very disappointing. It's distressing when you think that it can take up to 15 minutes after a harpoon actually hits a whale for the whale to die. "It's even sadder when you consider there's a calf involved," Garrett told local television. Australia's Prime Minister Kevin Rudd has promised a stronger effort to try and stop Tokyo's cull, although both countries have agreed not to let Canberra's opposition to whaling "influence diplomatic negotiations". The Sea Shepherd group said they would try and accelerate their departure for Antarctica after the release of the pictures to launch more protest action. "We are anxious to get back as soon as possible and we are doing everything possible to stop them killing more whales," spokesman Tom Baldwin told Reuters.(Editing by Sanjeev Miglani)