SK Telecom has launched an upgraded mobile technology providing faster and more seamless data transfer service.

The nation's largest mobile carrier said Tuesday that it will initially launch the high-speed downlink packet access service in 25 major cities nationwide for eventual expansion to 84 cities by year's end.

The new service enables mobile phone users to download data much faster and thus hold seamless mobile communication.

Korea Telecom Freetel, the nation's second-largest mobile operator, will also launch the service next month in 50 cities.