The updated software, code-named Mango, will appear on new Windows phones beginning this autumn, and be available for existing Windows phone users before that, although Microsoft has not set a timetable for making the update available.

The update — announced eight months after the launch of Windows Phone 7 — involves 500 new features, including Internet Explorer 9 as the mobile browser, integrated Twitter and LinkedIn feeds, automated Facebook check-ins, and access to more than 17,000 downloadable applications.

The update improves Microsoft's distinctive "live tiles," which allow users to see real-time information on the phone screen without actually opening an application, and allows more than one application to run at the same time.

Microsoft said Acer Inc., Fujitsu Ltd. and ZTE Corp. were planning to bring new Windows phone devices to market, joining established handset makers Samsung Electronics, HTC Corp. and LG Electronics.

The new Windows phone handsets will be exclusively powered by Qualcomm Inc's second-generation Snapdragon mobile processors, the chip-maker said.

Microsoft is banking on the new version of its phone software to get its recent alliance with Nokia off to a strong start. The first phones made by Nokia using Windows software are expected late this year or early in 2012.

The two have some work to do to catch up with Google's Android, which now runs 36 percent of smartphones sold globally, followed by Apple with 17 percent, according to research firm Gartner.

Last quarter, Microsoft held only 4 percent of the smartphone operating system market, but was looking to convert the 27 percent market share held by Nokia's Symbian, which will be replaced by the Windows system in most of Nokia's new phones.