Amazon.com on Thursday launched a service that gives compact disk buyers instant copies of music in the Internet "cloud" in a major challenge to Apple's iTunes shop.

Amazon AutoRip provides free MP3 versions of music on CDs bought from the online retail titan.

Copies of tunes are stored in Cloud Player libraries on datacenter servers and can be streamed to an array of Internet-linked devices including smartphones or tablets powered by Android or Apple software and Kindle Fire tablets.

"What would you say if you bought music CDs from a company 15 years ago, and then 15 years later that company licensed the rights from the record companies to give you the MP3 versions of those CDs and then to top it off, did that for you automatically and for free?" Amazon.com founder Jeff Bezos asked rhetorically.

"Well, starting today, it's available to all of our customers - past, present, and future - at no cost."

Copies of music on any AutoRip CDs bought from the Amazon Music Store since it opened its virtual doors in 1998 will automatically be added to buyers' online libraries free of charge, according to Bezos.

Amazon boasted of having 50,000 albums available at AutoRip, with the list of artists including Adele, Green Day, Maroon 5, Susan Boyle and Michael Jackson.

Amazon in June released its music player app for iPhone and iPod touch, a move that expands the reach of the Internet retail giant for Apple users.

The Cloud Player app allows customers to stream or download music stored in Amazon accounts to the iPhone or iPod touch, play music that is already stored on their device, and manage or create playlists.

The Seattle, Washington-based company went on to add technology that scans people's iTunes or Windows Media Player collections and then adds matching songs to Amazon Cloud collections.