Microsoft has unveiled a touch-ready version of Office, the latest version of the company's market-leading productivity software suite.

In San Francisco, Microsoft CEO Steve Ballmer described Office 2013 as the firm's "most ambitious release" to date.

The software is primed for mobile devices, cloud computing, and social networking.

For the first time, Word, Excel, PowerPoint, and Outlook are all responsive to touch-screen controls - taps, swipes, and pinch-and-zoom can be used within documents, files and presentations.

The user-experience is designed to be more "immersive," "visceral" and "multimedia-rich" compared to earlier version of Office.

The other features are:

Documents, slides, and presentations can be marked up on mobile screens, drawn on, highlighted or annotated with a digital pen, stylus or even a finger.

Skype, bought for $8.5bn (£5.4bn) in 2011, and Yammer, a social network for businesses, are being rolled into Office: live, multi-party conversations and meetings can be created with Skype video and accessed within Word, PowerPoint, or Outlook.

New "People Cards" include an individual's digital "presence" - a photo, options to email, instant message, phone or video chat, and activity feeds from the social networks Facebook and Linkedin.

Skydrive automatically saves and syncs all Office documents in an online, cloud-based storage service. This makes files and content created in Office available on demand across computing devices.