SAN FRANCISCO (AFP) - US prosecutors on Monday unsealed indictments against six people suspected of collectively pirating millions of applications tailored for Android-powered mobile devices.

Criminal charges were levelled at leading members of "piracy groups" SnappzMarket, Appbucket, and Applanet, according to the US Department of Justice.

"Copyright infringement discourages smart people from doing innovative things," US attorney Sally Quillian Yates said in a release.

"This problem is especially acute when it comes to rapidly developing technologies, like apps for smartphones, and these defendants are now being held accountable for the intellectual property they stole."

The groups rented computer servers to host websites such as snappzmarket.com, appbucket.net, and applanet.net that stored and distributed pirated copies of copyrighted Android applications, according to the indictments.

Online domains for those websites were seized by authorities in August of 2012 in the first crackdown of its kind on mobile device app marketplaces, prosecutors said.

During the years prior to the Web addresses being seized, millions of dollars' worth of pirated mini-programs for Android-powered mobile devices were distributed by the websites, in what was portrayed as criminal copyright infringement.

"Today's federal indictments are the direct result of an extensive and thorough federal investigation into three groups of individuals aggressively engaged in and profiting from the theft of intellectual property," said special agent-in-charge J. Britt Johnson of the Federal Bureau of Investigation (FBI) Atlanta field office.

"The FBI will continue to provide significant investigative resources towards such groups engaged in such wholesale pirating or copyright violations as seen here."

Each of those named in the indictments lives in the United States.