The Wall Street Journal is reporting that Microsoft has approached Facebook with a view to buying the social networking site.

The news comes as Microsoft has ended its failed takeover attempt of Yahoo, leaving the company with $45 billion to spend, although Bill Gates recently stated there were no other acquisitions planned.

Microsoft already owns a 1.6% stake in Facebook after the software giant took a $240 million equity stake in a round of financing that valued the social utility at $15 billion back in October last year.

The reports suggest that Microsoft's bankers have put out "subtle signals" to Facebook, but not that active talks are ongoing. Facebook founder Mark Zuckerberg has always said he would be very reluctant to sell the site.