Apple Inc. was sued Wednesday over allegations its iTunes online music store and iPod music players are illegally using a patented method for distributing digital media over the Internet.

Atlanta-based ZapMedia Services Inc. sued Apple in U.S. District Court for the Eastern District of Texas, accusing the Cupertino-based company of violating two ZapMedia patents.

ZapMedia wants royalties on Apple's sales of iPods and iTunes music, which reached nearly $11 billion last year. The success of iTunes has helped make Apple the No. 2 music retailer in the U.S. behind Wal-Mart Stores Inc., according to market researcher NPD Group.

The patents in question cover a way of sending music and other digital content from servers to multiple media players, a broad description that could also apply to a wide swath of other companies selling digital media and the devices to play it.