MOTOROLA is returning fire in a legal battle with Microsoft, suing the software maker for infringing on 16 of its patents.

Motorola said on Wednesday that Microsoft's PC and server software, Windows mobile software and Xbox products infringe on its patents. The complaints were filed by its Motorola Mobility unit in the United States District Courts for the Southern District of Florida and the Western District of Wisconsin.

Last month, Microsoft Corp sued Motorola Inc for infringing on its smart-phone patents. It also filed a claim with the International Trade Commission.

Horacio Gutierrez, deputy general counsel at Microsoft, said the company is reviewing Motorola's filing but was not surprised by the move.