­The social website, Facebook, which alarmed investors by warning of negligible mobile revenues when it listed its shares has shown the fruits of its efforts in the area and said that in the third-quarter nearly a sixth of its revenue came from mobile advertising.

In the three months to the end of September, the company generated US$152.6 million in mobile advertising - compared to essentially zero revenues at the start of this year.

However, the company could also be generating a significant amount of mobile revenue which is not included in the above figure, thanks to adverts in the news feed that users scroll down to check on friends activities.

Facebook's CFO David Ebersman said that the company is now generating around $4 million in advertising per day from this newish revenue source, and that around three-quarters of that is coming from mobile users.

That equates to an annual revenue from mobile advertising in excess of US$1 billion - and would be additional to the conventional mobile ads the company is running.

Facebook also owns the Instagram service which is still ad free on the mobile version.