A long-anticipated free voice calling service has now been added to the Android version of WhatsApp, putting it in direct competition with the likes of Skype, Viber and Apple’s FaceTime.

The feature had initially been beta tested on a small number of users, after which it was available on an invite-only basis.

Calls can be made to a contact while chatting with them or by going through the contacts list within the app. If the user doesn’t have a version of the app supporting the feature, the caller is notified.

A tab for calls will appear next to the chats and contacts tabs, offering a list of incoming, outgoing and missed WhatsApp calls.

WhatsApp calls will also allow users to use the speakerphone and have mute options, as well call duration log.

However, emergency service numbers cannot be dialled.

Although WhatsApp has made no official statement about the news, the feature is also expected to come to iOS versions of the app, based on a comment made by co-founder Brian Acton at the Facebook f8 conference earlier this month.

In January, WhatsApp, which said it has hit 700 million monthly active users, introduced a web-based version of the messaging service, on which users can continue conversations they have on their phones in a desktop computer browser.