Taiwanese smartphone manufacturer HTC has accused Apple of patent infringement in its products including iPhones, iPads and Mac computers.
HTC has sought unspecified damages and a ban of use of the three patented technologies by Apple.
In a move that extends the ongoing dispute between the two companies, HTC filed a lawsuit in US District Court in the state of Delaware.
Last year in March, Apple had sued HTC for 20 patents infringement in the same court. Now Apple has repeated what it had said then: "Competitors should create their own original technology, not steal ours."
Apple sued HTC again this year in July.
HTC had said that it would "vigorously" fight against such claims.
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HTC general counsel had said, "HTC is dismayed that Apple has resorted to competition in the courts rather than the marketplace."
"HTC continues to vehemently deny all of Apple’s past and present claims against it and will continue to protect and defend its own intellectual property as it has already done this year."
After filing the lawsuit against Apple on Monday, HTC said, "We are taking this action against Apple to protect our intellectual property, our industry partners, and most importantly our customers that use HTC phones."
"This is the third case before the ITC in which Apple is infringing our intellectual property," the company added.
"Apple needs to stop its infringement of our patented inventions in its products."
Patent wars have hotted up, as mobile phone companies seek to get a bigger slice of the smartphone and tablet pie, which has grown significantly over the last year.
Creator of the tablet market Apple has sued many rivals including HTC and Samsung over patent infringements in several countries. The company is also facing counter lawsuits from rivals.
However, patent such cases usually end up in exchange of patent licenses.
Recently, Google bolstered its patent portfolio after buying over 1,000 patents from IBM and acquiring mobile manufacturer Motorola Mobility.
The search engine company, which provides the Android OS platform for smartphone makers, has accused Microsoft, Oracle, Apple and other companies of banding together to wage a hostile, organised campaign against its OS.
This week, Google announced plans to acquire Motorola Mobility for $12.5bn, in an apparent attempt to own more patents.
"Our acquisition of Motorola will increase competition by strengthening Google’s patent portfolio, which will enable us to better protect Android from anti-competitive threats from Microsoft, Apple and other companies," Google chief executive Larry Page has said.
