A Finnish anti-Internet piracy group said it received a bomb threat, allegedly from Anonymous, after it successfully forced a telecoms provider to block access to The Pirate Bay.
The non-profit group CIAPC (Copyright, Information and Anti-Piracy Centre) took the website to court in Helsinki last year on behalf of a Finnish recording industry association.
The court controversially ruled that Elisa, one of the largest telecoms operators in Finland, must block access to the Pirate Bay.
Elisa complied with the ruling on Monday, and CIAPC said it received an e-mail signed by Anonymous Finland shortly afterwards.
This said CIAPC's office in downtown Helsinki would be bombed this week, according to CIAPC, which has reported the e-mail to the police.
Anonymous, which the US FBI believes is mostly made up of young hackers, became famous for attacking the websites of Visa Inc and MasterCard in 2010.
Late last year, hackers affiliated to Anonymous published hundreds of thousands of e-mail addresses they say belonged to subscribers of Strategic Forecasting, a private intelligence analysis firm.
Mikko Hypponen, a cyber security expert who is head of research at F-Secure, noted the unique nature of Anonymous, which was more of a movement rather than a group. "Anyone who acts in the name of Anonymous becomes part of it," he said.
(Reporting by Jussi Rosendahl and Tarmo Virki)