Motorola Mobility Inc., a subsidiary of Motorola, said it sued Microsoft on Wednesday over patent infringement, according to an article in the Wall Street Journal. This makes up almost the third round of lawsuit filings between the two industry giants as Microsoft filed earlier last month over Android mobiles—mostly a royalties scuffle there. Now, Motorola has fired back, hammering Microsoft with more than a dozen patent infringement claims.

The mobile-phone handset maker said Motorola Mobility filed suits in the federal courts for the Southern District of Florida and the Western District of Wisconsin, alleging infringement of 16 patents by a variety of Microsoft products, including its PC and server software, Windows mobile software and its Xbox game-console products.

Motorola, based in Schaumburg, Ill., is “bringing this action against Microsoft in order to halt its infringement of key Motorola patents,” said Kirk Dailey, an intellectual-property executive at Motorola Mobility. “Motorola has invested billions of dollars in R&D to create a deep and broad intellectual property portfolio and we will continue to do what is necessary to protect our proprietary technology.”

The flurry of lawsuits may be the result of strained relations between Microsoft and Motorola over the use of technologies between the two corporations. While the two have come to some licensing agreements over the use of those technologies, Microsoft originally alleged that Motorola wasn’t playing fair.

Microsoft’s suit against Motorola covered some of the technologies used in Motorola’s Google Android handsets and this salvo comes also while the software giant attempts to press further into the mobile market. As the phone wars heated up this year, numerous companies with stakes in the industry have been filing legal briefs against one another, looking for a particular edge.