By Maggie Shiels
Technology reporter, BBC News, Silicon Valley
Apple's iPhone has over 16% of the market says analysts IDC
Taiwanese mobile phone maker HTC has filed a patent complaint against Apple, asking for the US sale of iPhones, iPads and iPods to be halted.
The move comes after Apple sued HTC in March, alleging it infringed 20 patents relating to the iPhone.
Meanwhile, the world's biggest mobile phone maker Nokia is also embroiled in a patent suit with Apple.
Analysts say firms frequently argue over patents, but the rows rarely lead to product bans.
In its case at the US International Trade Commission, HTC argued that Apple had infringed on five of its patents.
The firm asked for a ban on the importation of Apple's products, which are manufactured overseas.
HTC makes phones for Apple rival Google among others
"We are taking this action against Apple to protect our intellectual property, our industrial partners, and most importantly our customers that use HTC phones," said Jason Mackenzie, HTC's vice president for North America.
In March, when Apple launched its action, co-founder Steve Jobs put out a statement which said: "We can sit by and watch competitors steal our patented inventions, or we can do something about it.
"We've decided to do something about it."
Industry watchers are not surprised by the escalating patent disputes surrounding Apple.
"It's tit-for-tat to a degree because Apple sued HTC first and this is HTC fighting back," Van Baker of research firm Gartner told the BBC.
"Ultimately, the whole patent portfolio issue needs to be addressed and resolved.
"It is not uncommon to have potential patent infringements as new products come to market. Usually they are worked out via some cross-licensing deal but in the interim it is highly unlikely anyone will be shut out of the market."