Facebook will stop letting users send and receive private messages within its main smartphone app, and will require that users install a separate messaging app. During the next couple of weeks, European users -- and evebtually global users -- will have to install the company's standalone Messenger app in order to send and receive messages.

Facebook claims that its standalone Messenger app is faster than the messaging service that's currently built into Facebook's primary mobile app. It also offer more features such as the ability to make voice phone calls.

Facebook in February announced plans to buy the popular WhatsApp messaging app for $19 billion. One month earlier, the company launched Paper, a photo-heavy news-reading app.