Facebook has begun testing Facebook phone calls in the US and Canada to allow voice conversations through the social networking app Apple's iPhone, and soon Android and BlackBerry users.

This week, the company said in an email that it has extended a test that started in Canada earlier this month, bringing phone call capabilities to the Facebook Messenger app to the US too. Users can call friends for free over data networks instead of using up their minutes allowance, reports the Telegraph.

"We started testing this in Canada the first week of the year and today we're extending that test to the US," said Facebook. "We were able to expand the test so quickly because it went well in Canada and we wanted to expand the audience."

In order to make a call, the user simply needs to go into a Messenger conversation with the person they want to contact, then tap the 'i' icon and select 'Free Call'.

Facebook is expected to eventually expand the feature to include other countries such as the UK, and make it available for other operating systems.

The news follows Facebook's earlier announcement that it is rolling out a major new search engine called 'Graph Search', designed to give users more options in sorting through topics and interests based on their friends.

For instance, users can type in 'Italian restaurants in London my friends have been to', and Facebook will come up with a list of restaurants that your friends have checked-in to with some business information.

The tech community has also been abuzz since last year over rumours of a Facebook smartphone, which could implement the Facebook calls and Graph Search features, but no plans for a phone or any other type of hardware have been publicly discussed by the company.

Both Graph Search and phone calls are believed to be Facebook's attempt at increasing user engagement. "Facebook's worst nightmare is a static social graph; if users aren't adding very many new friends or connections, then their personal network becomes less and less active over time," Forrester Research's Nate Elliot told The Telegraph. "Terrifyingly for Facebook, the threat is very real: We haven't seen significant growth in the average number of friends per user recently."

Facebook's shares have fallen 21 per cent since they were first made available to the public for a price of $38 in May.

See also:

How your Facebook privacy settings impact Graph Search

Analyst: Facebook's Graph Search isn't a Google killer

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