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 were confident that its 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 Telekoms T-Mobile, the phones 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 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.