TOKYO, Japan (CNN) -- Anti-whaling activists are accusing a Japanese boat of destroying their vessel Wednesday by ramming into it during a skirmish in the Southern Ocean.
But Japanese authorities deny their boat intentionally rammed the activists' catamaran and said instead the incident happened accidentally when the activists were harassing their whaling fleet.
Sea Shepherd Conservation Society says its boat was ripped apart by the Japanese vessel during the incident.
"In an unprovoked attack captured on film, the Japanese security ship Shonan Maru No. 2 deliberately rammed and caused catastrophic damage to the Sea Shepherd catamaran Ady Gil," said a statement from Sea Shepherd.
The statement said six crew crew members, five from New Zealand and one from the Netherlands, were rescued by the crew of the Sea Shepherd ship Bob Barker. None of the Ady Gil crew were injured, the statement said.
The statement quoted the captain of the Bob Barker as saying the Shonan Maru No. 2 deliberately rammed the Ady Gil, ripping off eight feet of the bow of the vessel.
"The Japanese whalers have now escalated this conflict very violently," said Captain Paul Watson. "If they think that our remaining two ships will retreat from the Southern Ocean Whale Sanctuary in the face of their extremism, they will be mistaken. We now have a real whale war on our hands now, and we have no intention of retreating."
A Japanese Fisheries Agency statement blamed the conservation group for the incident.
"This is a continuation of the harassment of the Japanese research whaling program by Sea Shepherd and is extremely dangerous to threaten vessels and its crew. This is absolutely unforgivable," the statement said.
The incident continues an ongoing feud between conservation agencies and Japanese whaling fleets.
The Southern Ocean is a term used to describe parts of the Indian, Pacific and Atlantic oceans that surround Antarctica.
CNN's Yoko Wakatsuki and Kyung Lah contributed to this report.