Apple escalated its legal fight with Samsung by asking the US International Trade Commission (USITC) to block imports of some of the South Korean firm's smartphones and tablet computers. In a filing Tuesday, Apple asked the USITC to look into its complaint that Samsung is infringing on the California-based company's patents in "electronic digital media devices" including its Galaxy lines of smartphones and tablets. "Samsung has followed each of Apple's groundbreaking products with imitation products that incorporate Apple's technology and distinctive design," Apple counsel Alexander Hadjis said in the USITC complaint. Apple contended that the South Korean electronics giant was using its patented technology in components such as touchpads, software and audio interfaces. Hadjis branded Samsung "one of the principal infringers" of Apple intellectual property. Apple patents at issue ranged from headphone technology to "ornamental design features." Apple asked the independent, quasi-judicial federal agency to stop offending Samsung devices from being imported into the United States for sale. Samsung could not be reached immediately for a response Wednesday. Last week, Samsung asked the US ITC to ban the import of Apple products into the United States, expanding a patent war with the US mobile gadgets star. The ITC has been urged to stop Apple shipping its popular iPods, iPhones and iPads into the US market from where they are manufactured, a Samsung spokesman said. It accuses Apple of breaching patents related to wireless communications standards and mobile device user interface. "The complaint requests relief in the form of a permanent exclusion order prohibiting entry to the United States of all Apple products in violation of these patents," Samsung said in a statement. "Samsung will continue to actively defend our intellectual property." The latest action ramped-up the wrangling between the world's two fastest growing smartphone makers. The tussle began when Apple filed suit against Samsung in April in San Francisco, accusing the Korean firm of copying its smartphones and tablet computers. Samsung responded later that month with a lawsuit in Seoul alleging five patent infringements by Apple. It filed separate actions in Tokyo, citing two patent infringements, and in the German city of Mannheim citing three. Last month Apple lodged a second lawsuit against Samsung with a district court in Seoul, asking for a sales ban on Samsung's latest products. It accused them of copying the iPhone and iPad. Samsung's Galaxy Tab has been a huge-selling rival to the iPad, which has dominated the growing market for the touchscreen devices. Despite their prickly competition in finished products, the two firms have a close business relationship. Apple was Samsung's second-largest client in 2010 after Japan's Sony, accounting for four percent of the South Korean firm's 155 trillion won ($142 billion) annual revenue.