Microsoft's CEO Steve Ballmer made the announcement during a keynote speech at Mobile World Congress, which kicked off today in Barcelona.
The mobile version of IE9, which like the desktop browser will feature support for HTML5 and hardware acceleration, will be part of an update to handsets running Windows Phone 7, Microsoft's mobile OS that was launched last year.
However, it looks unlikely that the browser will be to be made available for any other mobile operating systems, such as Google Android or iPhone OS. The mobile web browser will be free and be offered as part of an update to the mobile OS.
Microsoft also revealed the mobile OS will also be updated to include multi-tasking – so users can run apps in the background while using others, as well as support for Microsoft's SkyDrive online storage service, as well as integrating micro-blogging service Twitter into Windows Phone 7's People Hub.
The first update, which will bring cut and paste features to the handset will be made available "in just a few weeks in early March", Ballmer said. The other features will be part of a second update to Windows Phone 7 expected later in the year.
See also: Nokia switches to Windows Phone 7