A cyber attack claimed by an activist affiliated with the hacking collective Anonymous shut down Japanese Prime Minister Shinzo Abe's personal website on Thursday. Messages posted to Twitter claimed the attack was in response to the country's whaling practices.

The attack comes after Japan sent two whaling ships to the Southern Ocean off the coast of Antarctica.

Commercial whale hunting has been under a moratorium since 1986 and is monitored by the International Whaling Commission, an intergovernmental organization that focuses on the conservation of whales and the regulation of their hunting by traditional indigenous groups. Although the practice is banned, Japan continues its annual hunt under the pretense of scientific research.

In late November, Anonymous hackers shutdown five government websites in Iceland, include the prime minister's and the ministries of the environment and interior, in protest of the country's whaling activities.

Japan's Chief Cabinet Secretary Yoshihide Suga said it was investigating the attack, according to the New York Times.

"We have not determined for certain that it was an attack by Anonymous, but we have received reports that they claimed responsibility," Suga said.

Abe's website was back online Thursday afternoon.