HTC has filed a patent infringement complaint against Apple with the US International Trade Commission, just two months after Apple filed a suit of its own against HTC.
HTC says Apple has violated five of its patents, and is calling for Apple to be banned from selling the iPhone, iPad and iPod in the US.
Two of the patents relate to smartphone power consumption, while the other three relate to the way a phone dials numbers from contacts stored in an address book.
"As the innovator of the original Windows Mobile PocketPC Phone Edition in 2002 and the first Android smartphone in 2008, HTC believes the industry should be driven by healthy competition and innovation that offer consumers the best, most accessible mobile experiences possible," said Jason Mackenzie, HTC's north American vice president.
"We are taking this action against Apple to protect our intellectual property, our industry partners, and most importantly our customers that use HTC phones."
In March, Apple listed 20 patents relating to touch-screen technology and mobile computing that it said HTC had infringed, in a move widely seen as an attack on HTC partner Google. There's a hearing scheduled for March next year.
Apple's also currently battling Nokia in the courts over cellphone patents.