Anti-whaling protest group Sea Shepherd said a Japanese whaling vessel "intentionally rammed" one of its protest boats today during a standoff in Antarctic waters.

The harpoon ship Yushin Maru 3 hit the protesters' vessel Bob Barker off Cape Darnley in Australia's Antarctic territory, penetrating its hull, the group said in a statement posted on its website.

Despite the incident, which occurred in the early afternoon eastern Australian time, the Bob Barker continued to try to block the activities of Nisshin Maru, the factory ship of the Japanese whaling fleet, the group said.

"No crew was injured during the collision. The Bob Barker continues to block the slipway of the Nisshin Maru, preventing the transfer of slaughtered whales and effectively shutting down illegal whaling operations," Sea Shepherd said in a statement.

The incident follows the sinking of another Sea Shepherd protest boat, the Ady Gil, during a collision with Japanese whalers in early January.