Anti-whaling activists have accused Japanese whaling ships of deliberately ramming one of their boats in the Southern Ocean, while the whalers have blamed protesters for the collision.

Activists from the environmental group Greenpeace have been hounding a fleet of Japanese whalers for several weeks in the Southern Ocean, southwest of Australia.

The collision between the Greenpeace boat and the Japanese ship is another confrontation in what has become a heated battle. Both sides blame the other for the crash, which left the Greenpeace ship, Arctic Sunrise, with a dented bow.

Japan's Institute of Cetacean Research accuses the protesters of deliberately ramming its research boat, the Nisshin Maru, while it was attempting to transfer cargo. In a statement, it urged Greenpeace to stop its "dangerous and criminal actions."

Greenpeace spokesman Shane Rattenbury says the group is not looking for a violent confrontation.

"We certainly came down here committed to peaceful protest and we've made it very clear to the owners of the whaling fleet back in Japan that it's our intention to protest their activities but to not harm any of their crew and we certainly have no interest in causing a collision at sea," he said. "It's far too dangerous. We're out here in the middle of nowhere. The water's freezing. If anybody was to end up in the water, they've got very little chance of survival."

Greenpeace says none of the 25 crew on board the Arctic Sunrise were hurt and the boat is still seaworthy. The Japanese also reported no injuries to crew members.

Activists have been chasing the Japanese fleet for three weeks to try to stop its whale hunt.

Whale hunting is banned, but whales can be taken for research under the rules of the International Whaling Commission.

Japan's whalers say the hunt for 850 minke whales and 10 fin whales is part of a scientific research program.

However, Australia and other countries believe the expedition in the Southern Ocean near Antarctica is simply a front for the commercial harvesting of whale meat, which is popular in Japan.