(CNN) -- Japanese whalers and anti-whaling activists clashed in the waters near Antarctica on Friday, with each side offering conflicting accounts of the confrontation -- the second between the two boats in a week.
The anti-whaling group Sea Shepherd Conservation Society's founder, Capt. Paul Watson, told CNN that two of his crew members were injured when crew members on the Japanese ship Nisshin Maru threw flash grenades aboard his ship, the Steve Irwin.
Watson also said he took a bullet to the chest while wearing a Kevlar vest. "We don't know where that bullet came from," he told CNN.
Japan's Institute of Cetacean Research, which runs the Japanese whaling ships, denied firing any shots.
"No one shot Paul Watson. His claim that we shot at him and he has the bullet that was stopped by his bullet-proof vest is more fiction for articles by the Australian media," said Minoru Morimoto, the director general of the institute, in a news release on its Web site.
The institute said it threw seven "sound balls," which it described as "harmless" explosive devices, after people aboard the Sea Shepherd threw bottles of butyric acid -- an acid found in rotten butter -- at the Nisshin Maru. Watch captain describe incident »
The Japanese Coast Guard had also given "clear and loud warnings to the Sea Shepherd vessel during two passes," the institute said. It did not describe the type of warnings.
The institute said it was "disappointed that more serious means were required today for defending its research vessels in the Antarctic."
But Watson accused the Japanese of changing their story.
"They admitted that they fired warning shots, and then they said that they didn't, so, there's a lot of contradictions," Watson said.
"We've also documented this with video and photographs, and the confrontation speaks for itself, really."
One photograph on the Sea Shepherd's Web site shows Watson, startled, looking down at his chest. The caption declares the picture was taken "immediately after he was shot."
Another photograph shows Watson holding two small objects -- a bullet and a "mangled" anti-poaching badge that Watson was wearing under a Kevlar vest, the group said.
The two other alleged injuries were not serious, according to the Sea Shepherd: 35-year-old Ashley Dunn injured his hip and Ralph Lowe, 33, of Melbourne, Australia, has bruises on his back.
The Sea Shepherd, a hardline conservation group, is "committed to the eradication of pirate whaling, poaching, shark finning, unlawful habitat destruction, and violations of established laws in the world's ocean," according to a statement on the group's Web site.
The group uses its boats to interfere with whaling and fishing boats, and its efforts have included ramming a Portuguese whaler, the Sierra, in 1979, according to the group's Web site.
On Monday, Itsunori Onodera, Japan's senior vice minister for foreign affairs, said four whalers aboard the Nisshin Maru suffered injuries after activists threw butyric acid onto the vessel.
He did not elaborate.
On Friday, Watson hailed the group's interference with the Japanese whaling ships as "very successful."
"We've been here since December 5, to shut down their whaling operations for a total of five weeks. They haven't even got half their quota, and so I think that it's been a very successful season."
He added, "We're trying to uphold the law down here."
In the early 1980s, the International Whaling Commission determined that there should be a moratorium on commercial whale hunting. Whaling is allowed under international law when done for scientific reasons, which Japan cites as the legal basis for its hunts.
Many in the international community -- particularly Australia -- believe that such hunts amount to needless slaughter. Critics say that Japan's research is actually a pretext for retrieving whale meat to be sold in markets and restaurants.
Japan is lobbying a dozen members of the International Whaling Commission in Tokyo to support its much-criticized Antarctic whaling program. The effort comes before all 78 members of the commission at a two-day London meeting that ends Saturday. Watch why Tokyo is furious over the stink between whalers, protesters »
The commission is meeting to discuss reaching an agreement on whale conservation rules.
Japan's Ministry of Foreign Affairs and its Fisheries Agency are making their case to officials from Angola, Eritrea, the Republic of the Congo, Guinea, Ghana, Malawi, Tanzania, Palau, Micronesia, Cambodia, Laos and Vanuatu. E-mail to a friend
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