Microsoft filed suit against Motorola on Friday, accusing the US handset maker of violating its patents in smartphones powered by Google's Android mobile operating system.

Microsoft deputy general counsel Horacio Gutierrez said Motorola's Android-based smartphones infringed nine Microsoft patents.

The patents in question relate to synchronizing email, calendars and contacts, scheduling meetings, and notifying applications of changes in signal strength and battery power, Gutierrez said.

Microsoft's complaint against Motorola was filed with the International Trade Commission and the US District Court for the Western District of Washington state, where Microsoft has its headquarters.

"We have a responsibility to our customers, partners, and shareholders to safeguard the billions of dollars we invest each year in bringing innovative software products and services to market," Gutierrez said in a statement.

"Motorola needs to stop its infringement of our patented inventions in its Android smartphones," he said.

Microsoft supplies its own mobile operating system to handset makers and is reportedly planning to unveil three Windows Phone 7 smartphones next month made by South Korea's Samsung and LG Electronics and Taiwan's HTC.

Patent lawsuits are a regular occurrence among technology giants.

Apple is currently being sued by Finnish mobile phone company Nokia for patent infringement and has fired back with a countersuit against Nokia.

HTC, a major handset maker, and Apple are also currently suing each other over patent claims involving Android-powered phones.

US business software maker Oracle has filed suit against Google, charging that its Android software infringes on Java technology patents held by Oracle stemming from its recent acquisition of Sun Microsystems.

In June, Canada's Research in Motion, maker of the Blackberry, and Motorola reached a settlement to their long-running patent disputes.

Google's Android operating system is used in an array of devices that have been gaining ground in the hotly competitive global smartphone market.

In a blog post, Gutierrez referenced the other lawsuits over Android.

"The rules of the road are long-established in the software industry, and fundamental to the industry's growth and economic impact is respect for others' intellectual property rights," he said.

"Our action today merely seeks to ensure respect for our intellectual property rights infringed by Android devices; and judging by the recent actions by Apple and Oracle, we are not alone in this respect," he said.

Microsoft's Windows mobile operating system has been losing ground in recent years to Nokia's Symbian, Apple's iPhone, RIM's BlackBerry and Google's Android.

According to research company Gartner, Symbian will hold a 40.1 percent operating system market share at the end of 2010 followed by Android with 17.7 percent, BlackBerry with 17.5 percent, Apple with 15.4 percent and Windows Mobile from Microsoft with 4.7 percent.

In June, Microsoft killed the "Kin," a line of mobile telephones aimed at young people it had unveiled just two months earlier.