Nokia has released Skype software for its N800 Wi-Fi tablet, so users can make voice calls over the Internet rather than the cellular networks.

The two companies announced the move when the N800 was launched at the International Consumer Electronics Show in January, and Nokia delivered it with an upgrade to the N800's software yesterday. Current N800 owners can download it from Nokia's site.

Skype, with a claimed 196 million registered users, has expanded from its roots as a popular PC-based free calling system and offers text messaging, video calling, and low-cost dialling to and from traditional phones. There are already Skype clients for mobile devices but some mobile phone operators try to block voice over IP calls because they can eat into their voice revenue.

The N800 doesn't have cellular connectivity, only Wi-Fi and short-range Bluetooth. So the device can access the Internet in a home or office, at a public hot spot or on a municipal Wi-Fi network, but not in the vast areas covered by cellular data networks. The N800 is available in the shops and Nokia's website for £279, or $399 in the US.

In addition to the Skype client, the new software includes an Adobe Flash 9 web browser plug-in and lets customers use larger capacity memory cards - up to 8GB.

The N800 has slots for Secure Digital (SD), MicroSD, MiniSD, MultiMedia Card (MMC) and Reduced-Size MMC cards. The Linux-based device also has a built-in camera and an on-screen touch keyboard and uses the Opera browser.