US customs officials began closing Web sites that offer pirated movies, fulfilling a promise to crack down on illegal downloads that Hollywood executives say cost the US economy more than $20 billion a year.

The Homeland Security Department’s Immigration and Customs Enforcement arm announced Operation In Our Sites yesterday at Walt Disney Studios in Burbank, Calif.

Federal agents seized nine Web site domain names, and assets from 15 bank, Paypal, investment and advertising accounts. They also served search warrants on four homes.

Greater enforcement is a lobbying priority for the entertainment industry, which has lost sales as consumers gain access to free music and movies on the Web. The Obama administration is intensifying efforts to rein in pirated movies and music, Victoria Espinel, the US intellectual property enforcement officer, told a Senate panel on June 23, vowing to shut non-US sites.

The domain names targeted by the feds include TVshack.net, movies-links.tv, now-movies.com, planetmoviez.com and filespump.com.

Motion picture piracy costs the US economy more than $20 billion annually, Barry Meyer, chief executive officer of Time Warner’s Warner Brothers unit, said in written testimony at the hearing. He estimated there were more than 1.78 million illegal downloads of “Sherlock Holmes,” which starred Robert Downey Jr., in the 30 days following its December release.