Skype is set to formally release on Thursday the latest version of its voice over Internet Protocol service, which includes call forwarding and downloadable ring tones, pictures and sounds.

Skype for Windows 1.4, first available in beta in August, lets callers forward incoming Skype calls to another Skype account for free. Users can also forward calls to up to three landline or mobile numbers for as little as 2 cents a minute, depending on the country, according to the company's chief marketing officer, Saul Klein.

Users can personalise the service by downloading pictures, sounds and ring tones. The new Skype version is designed to make it easy for people to import contacts from Microsoft Outlook directly into their Skype buddy lists and to make one-click calls to numbers and names from Internet Explorer and Outlook.

The new software is also easier to install, Klein said, taking less than three minutes with a "Getting Started Wizard."

Skype, which eBay said it plans to acquire for US$2.6 billion, faces formidable competition from Yahoo, Google, MSN and America Online, all of which are integrating or offering integrated voice with instant messaging.

Klein said Skype wasn't concerned about the competition, particularly given the fact that the service has 56 million registered users and has recently seen an additional 170,000 new registrations per day.

"We have a two-year lead in terms of features and functionality," he said. "And we feel that the fact that we have a very large user base, whose growth accelerated this month, gives us an advantage."