Microsoft sues Motorola over Android phones
Microsoft is suing Motorola alleging it has infringed nine patents in its Android phones.
The giant software maker said Motorola phones that use Google's Android software are based on Microsoft technology.
The functions include synchronizing e-mail, calendars and contacts.
Microsoft filed its lawsuit in a federal court as well as filing one with the International Trade Commission.
Microsoft said Motorola licensed some of its mobile technology from 2003 to 2007 but continued to use the technology without renewing the licence.
Its court filing specifically mentions the Motorola Droid 2 and the Motorola Charm smartphones, but Microsoft claims that the infringements were not limited to those devices.
It is the latest development in a web of legal actions in the smartphone business.
A Motorola spokeswoman said the company has not yet received a copy of the suit, but based on its strong intellectual property portfolio, plans to "vigorously defend itself".
The suit is the latest in a complicated web of legal actions between various phone makers and software firms over who owns patents to the technology used in smartphones.
Nokia began by suing Apple last year, and Apple subsequently sued handset maker HTC.
Oracle has filed a lawsuit against Google, accusing the search engine giant of infringing patents on its technology.
Oracle says Google infringed patents on its Java software while developing its Android operating system.