HTC Corp. retaliated against Apple Inc. on Wednesday with its own patent infringement complaint — and the patents come from a surprising source.

Three of the five patents that HTC says Apple is infringing on with its iPhone, iPad and iPod Touch were owned by patent troll Saxon Innovations LLC. HTC, the Taiwanese Google-phone maker, appears to have gotten the IP as part of a settlement with Saxon in the spring of 2009. The other two are HTC patents, including one that was issued Tuesday, which helps explain the timing of the complaint.

The countersuit before the International Trade Commission is a response to Apple’s volley of lawsuits against HTC in the ITC and Delaware District Court in March. Apple claims that HTC’s phones, which run Google Inc.’s operating system, infringe on 10 of its patents — sending a forceful message about the growing rivalry between Apple and Google in the smart phone market.

Since the March offensive, there has been a persistent question about how HTC would respond. The company has a much smaller patent portfolio than Apple (hundreds versus thousands), which can be like holding a butter knife at a gun fight.

HTC hired Finnegan, Henderson, Farabow, Garrett & Dunner and San Francisco’s Keker & Van Nest to defend it against Apple and its lawyers at Kirkland & Ellis.

The lawyers looked at HTC’s IP and came up with two patents on controlling the power levels in smart phones — including the one issued Tuesday — that it claims Apple’s iPhones infringe on.

The other three patents cover a “Telephone Dialler with a Personalized Page Organization of Telephone Directory Memory.” According to patent filings, Saxon transferred them to HTC on March 31, 2009 — the same day that HTC settled a complaint that Saxon, a patent troll funded by Altitude Capital Partners, had filed in the ITC.

An HTC spokesperson did not respond to questions Wednesday about the company’s deal with Saxon. Lawyers from Finnegan didn’t return calls seeking comment. And Robert Van Nest, the lawyer leading Keker & Van Nest in the charge for HTC, said he wasn’t authorized to comment.

Apple’s lead lawyer on the case, Robert Krupka from Kirkland, did not return a call seeking comment.

The ITC has become a popular venue for patent litigation because of its quick schedule. Although companies can’t win monetary damages, the ITC can block imports of products that are found to be infringing.

HTC hasn’t filed counterclaims in the district court case in Delaware, although Keker is seeking to transfer the case to California.