In a message recently posted on YouTube, the hacker group Anonymous ordered the Japanese government to refrain from hunting whales.

"This is not just a warning," Anonymous said in what appears to be the first verbal offensive the group has launched over the issue. It also urged Japanese not to "follow the idiotic belief of your government."

Tokyo is aware of the message, which was posted on the video-sharing website Wednesday, and is prepared for follow-up actions, a government official said.

The group criticized Japan for "actively participating in the destruction of marine life worldwide," and posted undated videos showing Japanese ships hunting whales with harpoons. Last year, Anonymous warned the government of possible cyber-attacks to protest any revision of the country's copyright laws.

The whaling town of Taiji in Wakayama Prefecture became a focus of international outrage in 2010 when "The Cove," a U.S. documentary that chronicled dolphin hunting by local fishermen, won an Academy Award.

The Sea Shepherd Conservation Society, a U.S.-based anti-whaling group, also has set its sights on Taiji's dolphin hunt. Sea Shepherd activists filmed hunting activities and uploaded video onto the Internet, while calling for protests and soliciting donations for their cause.