Business software company Yammer is to sell itself to Microsoft for more than $1 billion, it was reported today.

It was not certain when the deal would be completed and formally announced, the Wall Street Journal reported, citing a person familiar with the matter.

San Francisco-based Yammer declined to comment, while Microsoft could not be reached for comment outside regular US business hours.

Yammer, which began in 2008 and provides enterprise social networking services, has raised more than $142 million in venture capital funding.

It says it counts more than 80 per cent of Fortune 500 companies as clients, and is backed by PayPal co-founder Peter Thiel, who also invested in Facebook.

Reuters