The specific nature of the case, which according to Bloomberg was filed at the High Court on July 29, has not been revealed. The legal action comes just weeks after Apple filed a complaint with the US International Trade Commission (ITC) accusing HTC of infringing its patents.
In preliminary findings, the ITC revealed it believed only two of the ten patents relating to the iPhone had been infringed. The findings are now being reviewed by a six-member committee. A final verdict is expected on December 6. If the complaint is upheld, the US may ban some HTC phones being imported into the country.
HTC said it will "vigorously fight these two remaining patents through an appeal before the ITC commissioners who make the final decision" along with maintaining it has never infringed any of Apple's patents.
It’s not the first time the tech giant has hit out at HTC. In March last year, Apple filed a lawsuit alleging that HTC infringed 20 of its patents relating to the user interface and the underlying architecture and hardware of the iPhone. However, HTC retaliated by filing a complaint with the ITC claiming Apple infringed five of its patents. While it did not reveal the technology covered in the patents, it did ask the ITC to halt the importation and sale of the iPhone, iPad and iPod in the US.
HTC declined to comment on the lawsuit while Apple has yet to respond to the matter.