Apple is suing Samsung Electronics, accusing it of 'copying' its products.
Apple claims Samsung's Galaxy line of mobile phones and tablets copies the iPhone and iPad.
The BBC reports Apple's claims focus on Galaxy's design features, such as the look of its screen icons.
Samsung said it had conducted its own research and development and would contest the accusations.
As well as being a competitor, the South Korean group supplies Apple with microchips that are used in some Apple products, such as the A4 and A5 processors, as well as memory chips used in MacBook Pro computers.
The lawsuit was filed on Friday.
The BBC reports there is already a web of litigation among phone makers and software firms over who owns the patents used in smartphones.
Nokia has sued Apple, which in turn has sued handset maker HTC Corp.
In October 2010, Apple sued Motorola, saying its smartphones use Apple's intellectual property.