Skype for iPhone has already been downloaded more than one million times, around six downloads every second reports Skype in a Thursday blog post.

Skype for iPhone was released on Tuesday to great fanfare with the ability to sign into Skype from any WiFi spot and call friends and family for free or at a typically low rate.

"This is a phenomenal performance, and we’re confident that it’s one of the fastest-downloaded iPhone apps ever," said Skype blogger Peter Parkes.

Meanwhile Skype for iPhone has been blocked by Apple's partner Deutsche Telekom’s T-Mobile, the phone’s exclusive carrier in Germany, as the telecoms giant does not allow the use of voice-over-Internet programs (VoIP) applications on its network.

Deutsche Telekom AG spokesman Alexander von Schmettow told the Chicago Tribune that iPhone contracts from the company's T-Mobile unit have blocked VoIP applications since 2007.

Schmettow said such applications could slow down T-Mobile's network, although Skype lawyer Robert Miller insisted Skype for iPhone pose no threat to network performance.

Compatible for iPhone and iPod touch running iPhone Software Update 2.1, Skype for iPhone is available free from the Apple iTunes App Store.