Facebook has increased its revenue from mobile devices with more users now accessing the social network via smartphones and tablets than from personal computers, but its quarterly profits fell sharply compared to last year.

The company on Wednesday reported a $64m profit in the fourth quarter of last year, a steep drop compared with $302m 12 months earlier, while revenue grew 40 percent to $1.585bn.

Facebook said that its number of mobile users, at 680 million, increased by 57 percent from a year ago, surpassing the 618 million average who access the site from computers.

More than 600 million people used Facebook daily - a 28 percent increase from the previous year, with the rise driven by mobile, the company said.

"The big thing for us is we have more than a billion people using our product and we need to make Facebook really good across all devices they use," Mark Zuckerberg, co-founder and chief executive, said.

Eden Zoller, principal analyst at Ovum, said that the figures were a boost for a company that took a pounding last year after its stock listing fell flat.

"What stands out from Facebook's results is the centrality of mobile for its service strategy and growth," he said about the social networking site's 23 percent ad revenue which came from users accessing the site from mobile devices.

The company's shares - which fell by half following their debut in May but have since been on a steady climb - fell 3.46 percent to $30.16 in electronic trades.