The FBI said on Thursday it executed more than 40 search warrants in the United States as part of its investigation into cyber attacks allegedly by a group called "Anonymous" that had backed WikiLeaks.
The cyber attacks, known as "distributed denial of service," were targeted against major U.S. companies and organizations and the search warrants coincided with the arrest of five people by British police in connection with the alleged attacks, the FBI said.
Anonymous, a loose-knit collection of activists, has claimed responsibility for attacking the websites of companies such as Visa, Mastercard and Paypal, all of whom severed their links with WikiLeaks after it began publishing its massive trove of secret U.S. diplomatic memos.
WikiLeaks, which was founded by Australian-born Julian Assange, has disclosed classified U.S. diplomatic dispatches that included candid and embarrassing assessments of world leaders as well as classified documents related to the wars in Iraq and Afghanistan.
Anonymous accused the companies of trying to stifle WikiLeaks and rallied an army of online supporters to flood their servers with traffic, periodically blocking access to their sites for hours at a time.
WikiLeaks said it did not sanction the attacks, which Anonymous said were carried out of sympathy with the secret-spilling site's support for government transparency.
Elsewhere, British police arrested five people on suspicion of involvement in the cyber attacks.
The five males, aged from 15 to 26, were arrested early Thursday at their homes across the U.K.
Police said Thursday's raids were part of a police probe into Anonymous carried out together with law enforcement agencies across Europe and the United States.
Other arrests have taken place elsewhere: In the Netherlands, a 16-year-old suspected of being involved in the attacks was arrested in December, while a French official close to the investigation told The Associated Press that a young teenager they suspect of masterminding the attacks was arrested the same month.
The official, who spoke on condition of anonymity because of he was not authorized to talk publicly about the arrest, said that police had since released the 15-year-old but have confiscated his computer.
Sweden wants Assange extradited from Britain so he can answer questions over sexual assault allegations.