Sony's slimmer and cheaper PlayStation Portable (PSP) has racked up sales of 1 million units in its first two months on sale in Japan.

The second-generation PSP went on sale in Japan on September 20 and hit the million mark on November 22 - that's two weeks faster than the original PSP took to sell a million units, Sony said.

Compared to the original PSP, which went on sale in December 2004, the new model is 33 percent lighter and 19 percent thinner. It is also slightly cheaper and has a larger liquid crystal display (LCD) screen. An optional digital TV tuner is also available that allows users to tune into Japan's free-to-air mobile digital TV broadcasts.

In the run-up to the year-end shopping season Sony plans to put on sale two new bundles, the 'Deep Red Value Pack' and 'Deep Red 1 Seg Pack'. The latter includes the digital TV tuner and both will be available in limited numbers. Sony has been successful in the past in boosting sales of its PlayStation hardware with the introduction of limited availability models in different colours.

According to previously published sales estimates Sony managed to sell around 250,000 of the new PSP during its first four days on sale. In recent weeks sales have fallen back but are still doing well.

In the week from November 12 to 18 the PSP was the second most popular piece of games hardware sold in Japan, according to Media Create. The agency, which estimates national sales based on point-of-sales system data, said 65,609 PSPs were sold during the week. The leading Nintendo DS saw sales of 76,069 units.