TOKYO - A hacking group said Thursday it has crashed Prime Minister Shinzo Abe's official website to protest Japan's plans to hunt whales.

Chief Cabinet Secretary Yoshihide Suga told reporters that one of Abe's websites became inaccessible early Thursday and police were investigating. The site was restored by the evening.

Suga acknowledged that the Anonymous hacker group has posted a Twitter message claiming responsibility, but added authorities had not singled out the group as a prime suspect.

One of the group's twitter messages posted earlier Thursday criticized Japan over its whaling plans, and warned that Abe's website would be brought down.

"@AbeShinzo whaling is not cultural right! Your website is #TangoDown!" the messages said. The group has also retweeted anti-whaling messages and one urging Abe not to eat whale meat and go vegan.

The incident on Abe's site is the latest in a series of recent attacks on Japanese websites. The group has said they were responsible for dozens of earlier attacks.

The group most likely chose Abe's site "to get public attention and spread their message against dolphin and whale hunts, rather than causing a real damage," said Nobuhiro Tsuji, a cybersecurity expert at Softbank Technology Corp., who is monitoring Anonymous activity. "They think bringing down the prime minister's website could cause an impact."

Japan, despite protests from anti-whaling groups, last week resumed its annual Antarctic whale hunt, which it says is done for research, under a revised plan after the International Court of Justice found its earlier program unscientific.