WhatsApp has urged users to update their messaging app after concerns were raised that hackers could inject spy software on to phones via the call function.

The Facebook-owned company said the spyware was spread by an “advanced cyber actor”, and infected multiple mobile phones using a major vulnerability in the app.

The spyware, developed by the secretive Israeli spyware company NSO Group, has the ability to give hackers full access to a phone remotely, allowing them to read messages, see contacts and activate the camera.

WhatsApp confirmed that a “select number” of users had been victims and that the bug and that the bug affects all but the latest version of the app on iOS and Android.

On Tuesday, WhatsApp said it had referred the incident to the US Department of Justice. It has also informed Ireland's Data Protection Commission, its main regulator in the European Union, of a "serious security vulnerability" on its platform.