WASHINGTON  The Federal Bureau of Investigation said it had executed more than 40 search warrants in the United States on Thursday as part of an investigation into an international group of computer hackers who attacked corporate Web sites last year in a show of support for WikiLeaks.

The F.B.I. investigation is part of a larger international inquiry into a loose confederation of hackers calling itself “Anonymous” that coordinated the cyberattacks against the Web sites of companies like PayPal, Visa and MasterCard late last year after they severed ties with WikiLeaks.

Law enforcement agencies in France, Germany and the Netherlands have also sought to find members of the group. On Thursday, the authorities in Britain also executed several search warrants and arrested five people, whose ages were said to range from 15 to 26, accusing them of playing a role in the attacks.

WikiLeaks solicits and publishes leaked documents on its Web site. It gained prominence last year after it made public hundreds of thousands of classified United States military documents and videos from the wars in Afghanistan and Iraq. More recently, WikiLeaks has begun to make public some of more than 250,000 leaked State Department cables. For the most part, it has published only cables that were selected as newsworthy and redacted by a consortium of news organizations that obtained advance access to the database, including The New York Times.