LIVE FROM GSMA MOBILE WORLD CONGRESS 2014: Over-The-Top (OTT) player WhatsApp has sent shockwaves through the mobile industry by announcing it will soon launch a voice service in addition to its widely used messaging application.

Speaking during a Monday-morning keynote session at the Mobile World Congress, Jan Koum, the internet player’s chief executive, said WhatsApp plans to introduce the voice service in the second quarter of the year, and will initially cater to Android devices and iPhones before turning its attention to Windows and Nokia handsets.

“We think we’ll have the best voice product out there,” said Koum. “It’ll use the least amount of bandwidth and we’re going to optimise the hell out of it.”

WhatsApp has already shaken up the mobile industry with its free messaging application, currently used by some 450 million subscribers worldwide, and its latest move will pose a threat to operators that still generate most of their revenues from providing traditional voice services.

It also raises the prospect of Facebook becoming a major player in voice: last week, the social-networking giant announced a $19 billion takeover of WhatsApp as it looks to expand its presence in emerging markets.

Asked for his reaction to the WhatsApp announcement, Hans-Holger Albrecht, the chief executive of emerging-markets operator Millicom, gave a lighthearted reply but made no attempt to hide his concern.

“Around 70 percent of our revenue is from voice, so I hear that you’re coming but I say take it easy,” he told Koum on a panel session that followed the keynote presentations.

However, eager to present the internet player as a prospective partner for operators – rather than a strictly disruptive force – Koum also revealed that WhatsApp is planning a tie-up with Germany’s E-Plus, without providing further details, and is keen to work with other operators on generating value for consumers.

While WhatsApp has so far shirked advertising and complexity, news of the Facebook takeover has triggered speculation it will have to change its approach in future. Yet Koum insisted the messaging provider’s values would remain the same when it comes to launching the voice service.

“Marc Zuckerberg [Facebook’s chief executive] agrees that WhatsApp needs to remain independent,” he said. “We can only achieve our goal of getting to a billion users if we continue down the path we started on.”