One in every five minutes on a mobile phone is spent on Facebook

Facebook now accounts for one out of every five minutes people spend on mobile phones in the US, the social network revealed, as it unveiled second-quarter results.

Users also spend an average of 46 minutes a day on Facebook's apps, excluding the massively popular messaging service WhatsApp, with people making 1.5bn searches a day on the site. It has also indexed more than two trillion posts.

The figures announced by Facebook, led by founder Mark Zuckerberg, shows its growth in popularity, with 1.49bn monthly active users as of June 30, up 13pc from a year earlier.

Of these, 1.31bn accessed the service through mobile devices, a rise of 23pc.

"Mobile is the engine of our revenue growth," said chief financial officer David Wehner.

Revenue jumped to $4.04bn in the three months ended June 30, from $2.91bn in the same period last year. This would have been $330m higher had it not been for a strong dollar, Mr Wehner added.

^{Mark Zuckerberg}

However, net income attributable to stockholders fell to $715m, from $788m as total costs and expenses jumped 82pc to $2.77bn.

Most of this rise was due to stock-based compensation following the $19bn purchase of WhatsApp in February 2014.

Sheryl Sandberg, Facebook's chief operating officer, also said the huge increase in expenses was for "growth we need now and in the future".

"We're investing in the next set of services and what will be future investments like Messenger, WhatsApp and Oculus," she added.

Around 700m people now use Messenger to contact friends, and the app has been downloaded more than 1bn times on Android's operating system.

Macquarie Research analyst Ben Schachter said the costs and spending met expectations. "We think the company has a lot of opportunities ahead of it so we want to see them investing quite heavily in those investments," he said.

On Oculus, Facebook's virtual reality business, Mr Zuckerberg said that "immersive 3D content is the obvious next thing" after video, which has recorded huge growth on the website.

The company had warned that 2015 would be a year of heavy investment, but analysts have said these investments are likely to translate into significant revenue streams in coming years.

Mobile ads accounted for 76pc of Facebook's advertising revenue of $3.83bn in the second quarter, compared with 62pc in the same quarter last year.

The average price per advert rose 226pc in the second quarter, while total advert impressions declined 57pc.

Ms Sandberg said 40m small and medium-sized businesses are now on Facebook, with 2m advertising on the site.

The shares fell 3pc in after-hours trading after closing 1.8pc higher at $96.99.

Up to Wednesday's close, Facebook shares had risen 24.3pc this year, valuing the company at $276.4bn.

Facebook's positive results came just a day after rival Twitter saw its shares slump following disappointing second-quarter figures.

Twitter's shares fell 14.5pc on Wednesday following a freeze in user growth.