Software giant Microsoft Corp. said yesterday it would buy back up to another US$40 billion of its shares.

The company said a plan to this effect has been approved by its board.

The program expires on September 30, 2013, Microsoft said in a regulatory filling.

As of July 28, Microsoft had about 9.13 billion shares outstanding, according to the filling.

The Redmond, Washington-based company said it has completed its previous 40-billion-dollar stock repurchase program.

Microsoft shares rose US$1.22, or 4.9 percent, to US$26.38 in pre market trading.