Internet telephony champion Skype said Wednesday that its software has been downloaded more than 500 million times, taking its registered user base to 171 million users worldwide.

Skype was first introduced in beta form at the end of August 2003 and is used in almost every country around the world.

The VoIP provider generates revenue through its premium offerings such as making and receiving calls to and from landline and mobile phones, voicemail, call forwarding and personalisation including ringtones and avatars.