Apple is suing its rival Samsung Electronics for allegedly copying the design of its iPad and iPhone.
It claims Samsung's Galaxy range of mobile phones and tablet "slavishly" copy the iPhone and iPad, according to court papers.
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 allegations.
Galaxy products use Google's Android operating system, which directly competes with Apple's mobile software.
As well as being a competitor, Samsung 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 and alleges Samsung violated Apple's patents and trademarks.
Apple spokeswoman Kristin Huguet said in a statement: "This kind of blatant copying is wrong."
However, Samsung said that its products are a result of research and development carried out by the company.
"Samsung's development of core technologies and strengthening our intellectual property portfolio are keys to our continued success," the company said in a statement.
The Korean electronics maker also said that it will contest the allegations "through appropriate legal measures to protect our intellectual property".
John Jackson, an analyst with CCS Insight, said Samsung is essentially Apple's only real tablet competitor at this stage.
"It's clear that they do not intend to let Apple run away with the category," he said.
John Park, analyst at Daishin Securities, added: "This is more like a symbolic move by Apple that it is quite serious about rivals advancing, and it is trying to hold back its close competitors."
The global smartphone market is expected to grow by 58% this year and Android is forecast to account for about 39% of it, according to research firm Gartner.
The firm estimates that the tablet market is likely to quadruple to 70 million units in 2011. While the iPad will still dominate over the next three years, Gartner expects its market share to decline from 69% this year to 47% in 2015 as Android devices move in.
Apple is one participant in 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.
Apple is bringing 16 claims against Samsung, including unjust enrichment, trademark infringement and 10 patent claims.
In March Apple sued HTC alleging patent infringement over the iPhone.
In October 2010, Apple sued Motorola, saying its smartphones use Apple's intellectual property.