Apple has accused the smartphone maker HTC of infringing its patents, in the latest phase of the legal battle between phone and tablet PC makers. Apple has filed a complaint against the US International Trade Commission (ITC) seeking an inquiry by the panel into the matter. The news comes just weeks after Apple and Samsung accused each other of copying designs and technology. HTC is the world's third-biggest mobile phone maker, by stock market value. However, HTC has denied Apple's allegations. "HTC is dismayed that Apple has resorted to competition in the courts rather than the market place," said Grace Lei, HTC's general counsel. Growing rivalry The launch of products like iPhone and iPad saw Apple become the market leader in the smartphone and tablet PC market. Apple's success in quickly securing a large slice of the market, with fashionable products enjoying good demand from consumers, prompted several rivals to launch their own gadgets hoping to win a share of the fast-growing market. However, that resulted in relations between Apple and its rivals souring as the competition grew. Last year the American technology company filed a similar complaint against HTC accusing it of infringing as many as 20 of its patents. That prompted HTC to launch a counter attack, claiming that Apple was guilty of infringing patents held by the Taiwanese company. HTC went to the extent of seeking a ban on sales of iPhones, iPads and iPods in the United States.