A long-simmering dispute over digital copyrights between the Church of Scientology and its critics has boiled over in recent weeks after video clips turned up on the Internet from a 2004 interview by the church’s most famous member, actor Tom Cruise.

When Scientology officials complained the clips were copyrighted and requested their removal from YouTube and other websites, a shadowy organization of online troublemakers sprang into action.

The group known as “Anonymous” posted an eerie video on the Internet featuring a computer-generated voice announcing a campaign to destroy the church and calling for worldwide protests Feb. 10.

It was all for laughs, said a member who spoke on the condition of anonymity. But things are now getting serious. A series of cyber attacks the group claimed responsibility for slowed access to church websites and apparently shut down the main one, www.scientology.org, one day last month.

As of Friday, suspicious white powder was mailed to 23 church locations in Southern California, forcing 60 people to be cleared from buildings in Tustin and causing police to close part of busy Brand Boulevard in Glendale for two hours. Preliminary tests by the LAPD determined the powder was cornstarch and wheat germ.

The FBI is investigating whether the mailings were connected to the hacking. Shortly after the mailings were disclosed by authorities, a caller who identified himself as a spokesman for the group Anonymous told a Times reporter that the group was not to blame.

The incidents have drawn new attention to Scientology.

Critics of the religion are flocking to Anonymous postings on YouTube, the popular video-sharing site. Their campaign has sparked a debate among long-time Scientology’s opponents, who wonder whether the aggressive rhetoric and tactics, including illegal denial-of-service attacks on the church’s websites, help the cause by raising awareness of the religion’s controversial beliefs, or hurt it by using the same type of heavy-handed methods they accuse Scientology officials of employing against critics.

“I don’t know if anybody in Anonymous did this but Anonymous set themselves up to be targeted in this way . . .,” said Mark Bunker, who runs one of the leading websites criticizing the church, www.xenutv.com, and posted a video last week warning Anonymous to tone down its campaign.

“I hope it doesn’t hurt the larger critic community who have been speaking out for years about Scientology’s abuse.”

Scientology was founded in 1954 by science fiction author L. Ron Hubbard. It teaches that “spiritual release and freedom” from life’s problems can be achieved through one-on-one counseling called auditing, during which members’ responses are monitored on an e-meter, similar to a polygraph. The process, along with a series of training courses, can cost Scientologists tens of thousands of dollars.

Cruise has become an outspoken proponent of the religion. In 2004, he won the International Assn. of Scientologists Freedom Medal of Valor award and part of the ceremony included a taped interview with him talking about why the religion is important to him.

The video was posted on YouTube and other sites this month, leading the Church of Scientology to request its removal for copyright violation.

A Scientology spokeswoman said the church wasn’t trying to suppress the video, which it says can be watched at any of its facilities around the world.

But it was made for “the Scientology congregation” and “never intended for replay on television or the Internet,” spokeswoman Karin Pouw said in a written response to questions.

The requests to have it removed are similar to take-down requests by movie studios and TV networks, she said. But members of Anonymous were angered by the requests and decided to take on the church, said the group’s representative.

The group is a loose confederation of about 9,000 people who post anonymous messages in chat rooms on websites he would not identify. While they are experienced Internet users, few are computer hackers, he said. But there are enough people with knowledge of how to attack websites that they were able to launch the attacks, the spokesman said. One of the attacks, known as distributed denial of service, involves flooding a website with requests, overloading its capacity.

Pouw said Scientology’s websites “have been and are online.”

The Church of Scientology also shifted the company that hosts its site last week to Prolexic Technologies Inc., which specializes in stopping denial-of-service attacks.

jim.puzzanghera@ latimes.com Times staff writer Andrew Blankstein contributed to this report.