Facebook has bought the popular instant messaging service WhatsApp for $19 billion ($11.4bn) in a cash and shares deal.

The deal comprised $15 billion Facebook shares and $4 billion in cash. Founders and employees of WhatsApp will share $3 billion of the shares that will vest four years from now.

The deal, which Facebook chief executive Mark Zuckerberg described as “incredibly valuable”, is the social media firm's biggest to date and is part of a series of multi-million dollar purchases.

"WhatsApp is on a path to connect one billion people. The services that reach that milestone are all incredibly valuable," said Mr Zuckerberg.

"But WhatsApp is a very important and valuable worldwide communication network.

"In fact, WhatsApp is the only widely used app we've ever seen that has more engagement and a higher percent of people using it daily than Facebook itself."