Apple's busy legal diary keeps growing thicker, with new litigation against the Cupertino company that demands 12 per cent of its iTunes and iPod profits.

The computer firm has angered Hong Kong company Pat-Rights. The latter firm claims to own the patent of the digital rights management technology used in the iTunes Music Store.

Pat-Rights alleges that Apple is infringing on US patent 6,665,797: "Protection of software against unauthorized use". This was granted in 2003.

The patent describes a way to determine if identity information "is existing in a processing apparatus".

A European Patent (number 1242893) on the process was applied for in 1998, but this has not yet been approved.

Pat-Rights CEO Philip Tse said: "We have kept a close watch on every dvelopment of iTunes. We believe this is wilful infringement. Apple shows no respect to us and our patent rights."