Apple ratcheted up its legal fight against HTC with a second complaint filed with the U.S. International Trade Commission (ITC) yesterday.

A copy of the complaint was not yet available on the ITC's website, but Apple's latest filing shares the title of HTC's previous complaint against Apple, "Portable Electronic Devices and Related Software."

The ITC has not yet agreed to launch an investigation into Apple's new allegations.

HTC could not be immediately reached for comment, but company general counsel Grace Lei said in a statement provided to multiple media outlets that HTC "continues to vehemently deny" Apple's claims.

"HTC is dismayed that Apple has resorted to competition in the courts rather than the market place," Lei said, according to Reuters.

The ITC is investigating HTC's claims against Apple and is also investigating Apple's countersuit against HTC, which also files patent infringement charges against Nokia.

The commission's staff recommended in April that HTC and Nokia should not be charged with violating Apple's patents, but a final decision on that case from an ITC administrative law judge isn't due until August.

The ITC is expected to rule on HTC's complaint against Apple in September.