On the heels of Microsoft's second patent-related suit against Motorola filed Tuesday, Motorola has fired back with lawsuits of its own.

Yesterday, Motorola accused Microsoft of infringing 16 patents in its Xbox gaming console and in Windows for servers, PCs, and mobile devices, the company said. The accusations are in complaints filed in U.S. District Court for the Southern District of Florida and the Western District of Wisconsin.

The suit is one of a rash of patent cases that's broken out in the mobile-device market, with other combatants including Apple, Nokia, HTC, Google, and Oracle. Microsoft accused Motorola of infringing its patents in an October lawsuit' the second suit, filed Tuesday, accused Motorola of breaching its contract by overcharging for patents for wireless communication and video-decoding technology used in the Xbox.

Motorola has requested Microsoft stop using its patented technology and pay compensation. Here's Motorola's description of the patents it alleges Microsoft violates:

The Motorola patents directed to PC and server software relate to Windows OS, digital video coding, e-mail technology including Exchange, Messenger, and Outlook, Windows Live instant messaging, and object-oriented software architecture. The Motorola patents directed to Windows mobile software relate to Windows Marketplace, Bing maps, and object-oriented software architecture.

In a statement, Motorola issued the customary words touting its own intellectual property and regretting that Microsoft chose to bring its complaint to the courts.

"Motorola's R&D and intellectual property are of great importance to the Company and are renowned worldwide. We are committed to protecting the interests of our shareholders, customers and other stakeholders and are bringing this action against Microsoft in order to halt its infringement of key Motorola patents. 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," said Kirk Dailey, corporate vice president of intellectual property at Motorola Mobility. "It is unfortunate that Microsoft has chosen the litigation path rather than entering into comprehensive licensing negotiations, as Motorola has mutually beneficial licensing relationships with the great majority of technology companies industrywide."

Update 9:55 a.m. PT: Horacio Gutierrez, Microsoft's corporate vice president and deputy general counsel of intellectual property and licensing, had this response: "We are still reviewing Motorola's filing, which we just received. This move is typical of the litigation process, and we are not surprised. We remain confident in our position and will continue to move forward with the complaints we initiated against Motorola in the U.S. District Court for the Western District of Washington and with the International Trade Commission (ITC)."