Popular VoIP provider Skype has released its much-anticipated application for the iPhone, which users can now download from the Apple App Store. Skype for iPhone will be free for iPhone users to download, and will offer access to Skype's free calling and instant messaging services.

Second generation iPod Touch users can also access the service with a compatible headset and microphone. Essentially, Skype for iPhone subscribers will enjoy free Skype-to-Skype calls from any WiFi zone to other Skype users worldwide. Calls can also be made to landline or mobile phones from WiFi zones but these will charged at low rates.

Instant messages may also be sent and received between individuals with 3G, WiFi, GPRS or EDGE enabled handsets. Scott Durchslag, Skype's Chief Operating office, said that Skype software for the iPhone was the number one request amongst its users.

He commented: "Skype for iPhone will open up new ways for more than 400 million Skype users to stay connected and take their Skype conversations with them. "Skype for iPhone is an experience that offers the same simplicity, ease-of-use and quality our users have come to expect from Skype, combined with an elegance of design and richness so loved by Apple's many customers worldwide."

The application uses a WiFi, 3G, GPRS or EDGE connection to sign into Skype and utilise its services, depending on what is available when the user does so. However, when accessing Skype over the mobile internet, the company recommends an unlimited data usage plan - like that offered to iPhone users in the UK by O2 - to avoid extra charges.