Facebook ads have appeared on Zynga's website for the first time, as the company so far has been distributing ads only in its own website. The move indicates that the social network could launch an online advertising network to boost its revenue growth.

Currently, Facebook is showing ads and sponsored stories only on Zynga's web site but the company may be planning to create a full-fledged online ad network that distributes ads on other sites as well.

The company made most of its $3.7 billion in revenue last year from ads that appear on its site.

Facebook and Zynga were not available for comments.