WhatsApp CEO Jan Koum says the popular messaging application for smartphones, bought recently by Facebook, will soon be offering a voice service.

Koum said "we are going to introduce voice in WhatsApp in the second quarter of this year".

He made the announcement at the Mobile World Congress in Barcelona, Spain.

On Wednesday, Facebook acquired WhatsApp for $19 billion (£11 billion) in a deal that is by far the biggest by the social networking company and any other done by Google, Microsoft or Apple.

Koum says "there are no planned changes" to WhatsApp following its acquisition.