Image copyright Getty Images Image caption Facebook has been growing its mobile user base, a crucial metric for advertisers

Social networking giant Facebook has reported profits of $523m (£316m) and a 63% increase in revenue for the fourth quarter, beating expectations.

The boost in revenue was mostly due to stronger mobile advertising sales, a priority of boss Mark Zuckerberg.

Advertising revenue increased 76% from the same period last year, with more than half of that coming from mobile.

Overall, Facebook said it had 757 million daily global users as of December 2013.

For the full year for 2013, Facebook reported profits of $1.5bn and said its daily active users grew by 22%.

"It was a great end to the year for Facebook," said Mr Zuckerberg in a statement.

"We're looking forward to our next decade and to helping connect the rest of the world."

Facebook shares soared more than 10% in after-hours trading on the news.

Growing share

Facebook turns 10 years old next Tuesday, completing a remarkable transformation from a project started in Mr Zuckerberg's student room to a global empire with more than 1.23 billion monthly users.

Two years ago, Facebook had no revenue from mobile advertising sales.

Since then, the firm has made a concerted push to spruce up its mobile app in order to woo users and advertisers.

"2013 was the year we turned our business into a mobile business," said Mr Zuckerberg in a call to discuss the earnings.

According to research firm eMarketer, Facebook had a 16% share of all mobile advertising dollars spent in the US this year, up from 9% in 2013.

This comes after Facebook surpassed Yahoo as the number two digital advertising seller in the US.

Globally, Google is still the dominant player, with a 32.4% share of the $117.6bn spent on digital advertising in 2013.

Picture perfect?

On the call to discuss earnings, Facebook executives also highlighted two big Facebook apps: Messenger and Instagram, which Facebook bought for $1bn.

Chief financial officer David Ebersman said Instagram doubled its user base, but did not name specific figures.

Mr Ebersman declined to discuss the advertising load on Instagram, saying: "We're just really early with Instagram... We're going to move slowly because we think that's the right thing to do."

Mr Zuckerberg also highlighted the growth of Facebook's Messenger, saying the number of users was up 70%. He did not break down usage by region.